Document:

<PAGE>

                                                                   EXHIBIT 10.15

SpeechWorks International, Inc. has omitted from this Exhibit 10.15 portions of
the Agreement for which SpeechWorks International, Inc. has requested
confidential treatment from the Securities and Exchange Commission.  The
portions of the Agreement for which confidential treatment has been requested
have been filed separately with the Securities and Exchange Commission.

                                                                   June 29, 2000

SpeechWorks International, Inc.
695 Atlantic Ave.,
Boston, MA 02111
Attention: Joe Murphy

Dear Joe;

     This letter ("Letter") will serve to confirm that NET2PHONE, INC. ("N2P")
and SPEECHWORKS INTERNATIONAL, INC. ("SWI") are entering into a business
relationship whereby:

(i)   N2P has agreed to invest $4.0 million in SWI pursuant to the terms of that
      certain Common Stock Purchase Agreement dated as of even date herewith
      (together with the other agreements contemplated thereby);
(ii)  SWI will provide to N2P certain software as described in Exhibit A-1,
      attached and made a part of this Letter;
(iii) SWI will provide certain professional services, including but not limited
      to, (a) platform integration and (b) application development in connection
      with N2P's global VoIP network; and
(iv)  the parties may pursue certain joint marketing efforts as further agreed
      upon in an executed License Agreement proposed in this Letter.

     Part I of this Letter is intended by the parties to be binding and Part II
of this Letter  shall be non-binding and expressly subject to the execution and
delivery of (1) a definitive Professional Services Agreement (the "PSA") and
Statement(s) of Work ( an "SOW") which shall be executed and delivered no later
than [    ], or a subsequent date as extended and mutually agreed upon by the
parties (the "Contract Date"). If for any reason the parties are unable to
consummate the License Agreement (as defined below) and the PSA, by the Contract
Date, the obligations set forth in this Letter, including but not limited to
Part I, and in that certain Non-Disclosure Agreement dated as of
_______________, 2000 ("NDA"), by and between the parties, the terms of such NDA
which by their nature survive, then either party may, upon written notice to the
other, terminate this Letter, and in the event of such termination, the parties
agree that Net2Phone's sole obligation and SWI's sole and exclusive remedy shall
be that Net2Phone shall pay SWI the License Fee as described in Paragraph A
below in the amount of [      ] US Dollars ($[      ]) and all reasonable
professional service fees accrued hereunder as of the date of such termination,
under the current fee schedule as described in Exhibit C, attached and made a
part hereof.

                                                                          Page 1
<PAGE>

Part I.  BINDING TERMS.

         A.  License Fees.

         (1) Initial Order. N2P hereby agrees to pay to SWI an amount equal to
             [] Dollars ($[]) in consideration for the grant of a license (the
             "License Fee") to N2P of the SpeechWorks software set forth on
             Exhibit A (the "SWI Software"). The terms of the license would be
             contained in a mutually agreed upon Master Software License
             Agreement ("License Agreement"), a draft form of which has been
             provided to N2P and which the parties agree to negotiate the terms
             of such License Agreement in good faith with the intent to execute
             and deliver said License Agreement no later than the Contract Date.
             The License Agreement would have a term of [] ([]) years (the
             "Term"). The $[] License Fee described in this paragraph A is a
             guaranteed and non-refundable payment.

             (1)  Subsequent Orders. Notwithstanding SWI's then-current fee
                  schedule, SWI agrees taht for the Term of the LIcense
                  AGreement, for all subsequent orders received during the
                  initial [ ] year term (counting the [ ] ([ ]) Ports ordered in
                  the initial order), the following perport discount schedule
                  shall apply.

                  AGGREGATE NUMBER OF PORTS IN THE INITIAL TERM   PRICE PER PORT
                  ---------------------------------------------   --------------
                  [     ] - [     ]                                  $[    ]
                  [     ] - [     ]                                  $[    ]
                  [     ] - [     ]                                  $[    ]
                  [     ] - [     ]                                  $[    ]
                  more than [     ]                                  $[    ]

              B.  Revenue Share. In addition to the provisions described above,
                  the parties hereby agree that the License Agreement shall
                  contain the following provisions regarding the sharing of
                  revenue.

                  GENERAL

                  N2P and SWI will share net revenue, as defined hereunder
                  generated by or through the Facilities Services (defined
                  below), as further defined in the proposed License Agreement
                  and as outlined below. In accordance with the License
                  Agreement revenue will only be comprised of those fees due to
                  [   ] from [    ] to [    ] by [    ].

                  In addition to the foregoing license fees, N2P agrees to pay
                  to SWI the following fees (the "Utilization Fees") for each
                  [ ] in connection with the [ ] (the "Facilities Services").

                        (1) [ ] percent ([ ]%) of any net revenue N2P derives
                            directly from [ ] or [ ] ("[ ]"); and
                        (2) [ ] percent ([ ]%) (net of the costs outlined in
                            Exhibit B; "Infrastructure Costs") for all revenue
                            derived from [ ] (or [ ]).

                                                                          Page 2
<PAGE>

                  Further, in the event that either of the following conditions
                  occur (in a manner to be verified under procedures to be
                  agreed to in the License Agreement) the applicable [] terms
                  set forth below would apply:

                         1. [] into an [] that []; or
                         2. [] to [] a [] or [] or [] with [.]

               In the event that the applicable condition precedent above is
               satisfied, N2P would pay to SWI an amount equal to:

          (1)  [] percent ([]%) of any net revenue N2P derives directly from
               [] or [("[]")]; and
          (2)  the lesser of (x) $[] per [  ] and (y) []% (net of the costs
               outlined in "Infrastructure Costs") for all revenue derived from
               [] (or []).

       Each N2P customer-specific [] transaction would provide for [] ([]) years
       of payments to SWI and such obligation  may survive the expiration of the
       [] ([  ]) year term of the License Agreement.

                                                                          Page 3
<PAGE>

         C.  Most Favored Pricing

                The following fee provisions shall apply to the License Fees,
                SWI professional services fees requested by N2P, and text-to-
                speech (TTS) (if and when available) licenses which may be
                contracted by N2P in the License Agreement or in any mutually
                agreed upon agreements. During the term of the License Agreement
                or any other agreement mutually agreed upon between the parties,
                SWI agrees that it shall provide the [] to N2P [] in a
                transaction (considering all relevant material terms) in which
                [] or []. In the event that SWI [], it shall thereafter [] and
                [] and [] to be [].

         D.  Roll Over Rights

                SWI hereby agrees that the covenant set forth in Section C above
                with respect to license fees shall be extended to all entities
                of which N2P owns (or acquires such interest in during the
                Term), at the relevant time, more than []% of the voting shares.
                Further, in the event that N2P owns an equity interest in a
                third party which is []% or less, then:

                    (i)  in the event that such third party is already a
                         customer of SWI, then SWI agrees that it shall allow
                         (1) such third party to pay to SWI the difference
                         between (x) the [] fees [] ([]") and (ii) the [] fees
                         [] and (2) [ ] to pay []; and
                    (ii) in the event that such third party is not already a
                         customer of SWI, then SWI may in its discretion enter
                         in to a license agreement with such third party and in
                         the event that such third party and SWI agree on the
                         applicable license fees, then N2P shall [] fee [] as
                         contemplated by clause (i) above.

                The parties agree that the revenue share provisions set forth
                above shall apply to any party described in this Section D which
                is licensing SWI software or using the Facilities Services.

            E.  Professional Services.

                (1)  Retainer. In order to secure the commitment of SWI Ito
                     provide certain professional services, N2P hereby agrees to
                     pay to SWI an amount equal to [] Thousand US Dollars ($[])
                     under the PSA ("Retainer"). Unless otherwise agreed upon by
                     the parties in the PSA or an applicable SOW, this amount is
                     subject to the terms of Paragraph F below, shall be due and
                     owing to SWI no later than [] regardless of whether N2P
                     accrues services fees in such amount prior to such date.
                (2)  Work Authorization. Upon execution of this Letter, N2P
                     shall be deemed to have authorized SWI to commence certain
                     professional services activities as directed by N2P related
                     to the initial project, and N2P agrees to pay SWI for
                     services rendered in accordance with its current fee
                     schedule up to an amount not to exceed the Retainer
                     described above. Any amounts accrued under this interim
                     Work Authorization section will be applied against the fees
                     agreed to in the applicable SOW. Additionally, any travel
                     expenses accrued may be billed for the amount incurred,
                     assuming that any required travel is approved in advance by
                     N2P. In the event N2P and SpeechWorks execute a mutually
                     acceptable PSA, such PSA will fully supersede, and make
                     null void, this paragraph (2). N2P acknowledges and agrees
                     that any deliverable developed in connection with the
                     services rendered hereunder shall not be delivered to N2P
                     until such time as a PSA has been executed.

                                                                          Page 4
<PAGE>

            F.  Unused Services Fees Allowance. In the event that the aggregate
                fees accrued for the project(s) covered under an initial SOW, if
                any, equal an amount less than [] Thousand US Dollars ($[]), SWI
                shall allow N2P to apply the balance thereof to the purchase of
                additional licenses under the terms of the License Agreement;
                such application, if any, shall occur no later than [ ].

             G. Joint Obligations. Each party agrees it may undertake the
                following marketing and publicity activities in order to
                promote the relationship:

                o  CUSTOMERS - Each company agrees to explore the use of their
                   existing customers to identify interested implementers of
                   the Voice ASP service.

                1. CO-MARKETING - N2P and SWI  will work together, in good
                   faith, to use commercially reasonable efforts to perform
                   the following:

                o  N2P and SpeechWorks will work together to issue a formal,
                   joint press release on the equity investment, and N2P will
                   also supply a quotation to be used in the Open Speech Web
                   announcement (to be complete Wednesday, June 28th)
                o  N2P and SpeechWorks will jointly participate in press and
                   analyst briefings regarding Net2Phone's equity investment in
                   SpeechWorks
                o  N2P will promote the "[]" program in relevant Marketing
                   promotions and collateral
                o  SpeechWorks will promote the N2P Voice ASP service in
                   relevant Marketing promotions and collateral
                o  N2P and SpeechWorks agree to work together for joint
                   promotion of the N2P Voice ASP commercial launch and
                   subsequent Voice ASP (post-GA) milestones
                o  N2P and SpeechWorks agree to make to cite each other in
                   relevant press releases and/or announcements. Specifically:
                   o  SpeechWorks will cite N2P as an investor-partner,
                      ASP-provider and provider of yet-to-be-specified speech-
                      based services where commercially appropriate,
                   o  N2P will cite SpeechWorks in announcements relating to
                      their speech-based initiatives where commercially
                      appropriate.

                                                                          Page 5
<PAGE>

Part II. NON-BINDING TERMS. The following terms are agreed by the parties to be
non-binding and shall only express the intent of the parties as to activities
which shall only be agreed upon in a definitive License Agreement, PSA and
Applicable SoWs.

                1. CROSS-MEDIA PROMOTIONS & ATTRIBUTION:  Subject to prior
                   written approval, not to unreasonably withheld or delayed:

                o  Each company can use the other company's logo/name in any
                   web listings (i.e., customer/partner lists)
                o  N2P agrees to work  with SpeechWorks to pursue cooperative
                   advertising with both parties contributing equally to the
                   associated costs.
                o  N2P agrees to SpeechWorks' usage of the N2P logo on demand-
                   generation vehicles (WSJ advertising, other advertising,
                   direct mail, etc.)
                o  N2P agrees to let SpeechWorks use the N2P name and logo in
                   IPO-related filings (eg: S-1)
                o  N2P agrees to participate in the SpeechWorks Conversations
                   User/Partner conference in Laguna Niguel, CA, as a speaker

                2. REFERENCABILITY:  Pending N2P satisfaction with SpeechWorks
                   performance against measurable success criteria and N2P
                   internal policies, N2P agrees to be a reference for i.) other
                   SpeechWorks prospects. Additionally, at N2P's sole
                   discretion N2P may participate in a Case Study

               3.  STANDARDS SETTING:  N2P and SpeechWorks agree to work
                   together jointly develop, market, and offer as De Facto
                   Standards to the market:

               o   VoiceXML and voice browsers
               o   SpeechLinks
               o   SpeechCookies
               o   Content and scripting tools
               o   SpeechSpot U.I. spec and implementation

               The parties agree that the following terms would provide the
               basis for an initial SOW:

               A. PLATFORM INTEGRATION SERVICES: SWI shall perform the
                  following with the reasonable cooperation of N2P:

               1. Convert Audio Driver to use N2P protocol and convert IP
                  packets into u-law PCM. This would essentially be re-writing
                  of Prompt DLL and Record DLL
               2. Switch the TTS API to use SWI implementation of Lucent TTS.
                  Done through SAPI.
               3. Provide an operational VXML browser. SWI will ship voice
                  browser source code to N2P.
               4. Provide training on any SWI implementation of VXML, in
                  classroom setting
               5. Provide tools to convert applications to VXML operation. SWI
                  will make available to N2P all internal tools that are
                  currently used as well as any commercially sold tools when
                  they are general release.
               6. Provide SpeechWorks licensed software and the VMXL browser
                  software on SCO Unixware 7.
               7. Support SpeechLinks as a platform capability for Net2Phone
                  speech services

SWI agrees that any costs associated with SWI's performance obligations, shall
be at SWI's sole expense.

                                                                          Page 6
<PAGE>

               B. APPLICATION DEVELOPMENT

                  1.  Provide interface documentation and assistance with the
                      implementation of the namedialer module (database, grammar
                      generation and storing and again the TTS interface) in
                      order to enable N2P personal voice dialing application.
                      This will be delivered from SWI solutions group and follow
                      the SADL process as with all application development
                      projects. This will need to have a SCOPE OF WORK defined
                      in order to accurately describe exact costs and time
                      estimates for delivery.
                   2. Provide Speech Site for internal use
                   3. Speech Web Directory - provide infrastructure for N2P to
                      run the application to enable any organization to
                      register their site in Open Speech Web Directory.

                   Part II of this Letter is non-binding and is intended to
                   facilitate negotiation and preparation of the License
                   Agreement and PSA that will embody the final understanding
                   between the parties. Except as otherwise specifically
                   provided for herein, the obligations of the parties to
                   consummate the transaction contemplated by this Letter shall
                   be subject in all respects to the negotiation, execution and
                   delivery of a definitive License Agreement and PSA .
                   Notwithstanding the foregoing, the $[] License Fee payment
                   obligation of N2P set forth in Paragraphs 1A of Part I is
                   agreed to be binding.

                   Please indicate your acceptance of the terms hereof by
                   signing the enclosed copy of this Letter on the line provided
                   and returning it to the undersigned.

                                                 Net2Phone, Inc.

                                                 By:  /s/ Jon Fram
                                                      ------------------------
                                                      Name:  Jon Fram
                                                      Title: President

Acknowledged and agreed:

SPEECHWORKS INTERNATIONAL, INC.

By:  /s/ Stuart R. Patterson
     ------------------------------
     Stuart R. Patterson,
     President and Chief Executive Officer

Date: June 29, 2000

                                                                          Page 7
<PAGE>

                                   EXHIBIT A
                                   ----------

                                 Initial Order

<TABLE>
<CAPTION>
PRODUCT NAME           PRODUCT DESCRIPTION            RECOGNITION       SYSTEM      FEE/PORT OR        LICENSE
                                                         PORTS          SEATS           SEAT            FEES
------------------------------------------------------------------------------------------------------------------
<S>           <C>                                     <C>               <C>         <C>                <C>
[    ]         Includes:                                  [  ]           N/A           $[  ]            $[  ]
               o  [    ]
               o  [    ] (see description above).
------------------------------------------------------------------------------------------------------------------
[    ]                                                                                                   N/A
               Includes:                                  N/A             1
               o  [    ] ([              ])
               o  [    ] ([              ])
------------------------------------------------------------------------------------------------------------------
</TABLE>
                                                       TOTAL LICENSE FEES: $[  ]

The term "Recognition Port" shall mean the number of telephone channels enabled
with the software included in SpeechWorks DialogModule Bundle B that is capable
of either recognizing spoken words or performing "barge-in" for a discrete
period of time. SWI acknowledges that telephone lines or ports can be configured
with or without speech recognition dynamically, and as such, charges are based
on the maximum number of simultaneous speech recognition ports currently
configured in the total system.  The term "system seats" shall mean the number
of end-users permitted to concurrently access and use, at the same time, the
SpeechWorks Tools and Grammar Libraries.

PAYMENT SCHEDULE:

The License Fee to be paid by N2P under the License  Agreement shall be due and
payable within thirty (30) days from the date appearing on an applicable invoice
prepared and delivered by SWI to N2P following the execution of the License
Agreement between the parties. If mutually agreed upon in the License Agreement
SWI may impose a late fee of 1.5% per month on any amounts which remain unpaid
thirty (30) days after they are due.

                                                                          Page 8
<PAGE>

                                  Exhibit A-1
                        DESCRIPTION OF LICENSED SOFTWARE

SpeechWorks(R) is a solution for speech-enabling transactional applications over
the telephone. packaged as six functional components:

     1.  SpeechWorks SMARTRecognizer(TM) recognizes words or phrases from
     individual vocabularies in the call flow and provides processing of phrases
     and sentences. This engine supports a range of hardware platforms and
     scales to thousands of phone lines. Its features include:

     2.  SPEECHWORKS DIALOGMODULES(TM) are high-level building blocks
     representing frequently used caller interactions that developers can
     assemble and integrate into applications. Each DialolgModule encapsulates a
     particular task such as capturing a "yes" or "no" response or creating a
     voice menu. The DialogModules are made available in three bundles/packages.

       A.  BASE:  Includes recognition kernel, reporting tools, and the
       following DialogModules:
       AlphaNumeric String - Collects a string of connected (pauses are not
       required) numbers and letters.  Patterns or a list of valid strings can
       be specified.
       Continuous Digits - Recognizes a string of connected digits only.
       Constraints such as string length or the allowed values can be specified.
       Item List - Lets callers speak words or phrases from a list (up to 250
       words), e.g. "Please say the name of the person you are calling?" or
       "What stock would you like to buy?"
       VoiceMenu - Lets callers choose a word or phrase from a list (maximum of
       20).  Menus are similar to ItemLists, but shorter so that the prompt can
       read each item to the caller.
       YesNo - Performs the essential function of identifying affirmative and
       negative responses from callers.

       B.  EXTENDED:  Includes Base DialogModules, recognition kernel, reporting
       tools, and the following DialogModules:
       CreditCardNumber - Collects a credit card number.  Can understand the
       major credit cards and many private label cards from retailers
       CCExpDate - Collects the expiration date for a credit card, usually month
       and year.  It recognizes the last day of a given month as well.
       Currency - Lets callers speak a monetary value in a natural way, e.g.,
       "One hundred twenty-five dollars and thirty two cents.  Non US dollars
       can be customized.
       Date - Collects dates in several formats, e.g., June Fourth or 6/4/70,
       nicknames can be mapped, e.g., Christmas or today, allowing callers to
       speak a date in a natural way
       ItemList - Up to 2,500 words
       NaturalNumbers - Collects whole numerical amounts; callers can say "fifty
       four hundred".  Vocabulary for units can also be added, as in "a thousand
       boxes".
       SocialSecurityNumber - Collects a 9-digit US Social Security number.
       Illegal numbers, such as those beginning with three zeroes, are screened
       out
       Spelling - Recognizes individual letters so that callers may choose to
       spell out a request.

                                                                          Page 9
<PAGE>

       TimeOfDay - Collects a naturally spoken time of day.  Callers can use 12-
       hour or 24-hour times, as well as prefix words such as "about" and
       "around"
       TelephoneNumber - Collects a phone number in the "North American
       Numbering Plan" consisting of ten, seven or three digits.  It allows
       common phrases such as "area code" and "one eight hundred".
       ZipCode - Recognizes a five and/or nine digit United States ZIP code

       C.  PROFESSIONAL NL (NATURAL LANGUAGE): Includes Extended DialogModules,
       recognition kernel, reporting tools, and the following DialogModules:
       ItemList - Greater than 2,500 words or phrases
       CustomContext - Provides the ability to run the results of custom
       modules created with the Software Development Kit.
       The Professional NL will typically require some level of SpeechWorks
       custom development services or development support.
       Name - Available with Release 6.0 making it easier to collect a person's
       first, last or first and last names where the names are completely
       unknown.  Speech Attendant apps should continue using the ItemList
       DialogModules

     3.  SPEECHWORKS REPORTING AND ANALYSIS TOOL is bundled with each of the
     DialogModule packages. The tool generates text diagnostic reports about
     applications based on call logging data. The reports included are:

       Call-Start - displays a percentage breakdown by one hour time period of
       when calls are initiated helping to identify peaks in system usage.
       Call-Length - displays a percentage breakdown of calls by duration
       tracking the efficiency of user interface improvements that result in the
       reduction of call length.
       Module Transaction Results - summarizes execution results for each
       DialogModule presenting an overall success rate.  Success rates lower
       than 90% indicate problem areas.
       Module Callflow Results - summarizes results of each attempt to collect
       the primary DialogModule data from the caller.  High values for denied
       confirmation and rejection indicate that recognition is not performing
       well.
       Context Results - summarizes the result of each recognition event.  This
       report illustrates a complete picture of the caller experience at the
       transaction level.
       Module Vocabulary Results - summarizes results classified by the answer
       returned by the recognizer via a DialogModule.  This report can be used
       to give an indication of a) how effective the system recognized a
       caller's utterance and b) how easily callers were able to clarify/confirm
       what was said.
       Context Stats - summarizes various additional statistics for each
       recognition context.  This report allows quick identification of problem
       contexts indicating that improvements are required

     4.  SPEECHWORKS SOFTWARE DEVELOPMENT KIT (SDK) includes the following suite
     of editors and utilities for configuring DialogModules, providing service
     management functions, and supporting ongoing tuning and maintenance:
     Vocabulary Editor (VED), Grammar Development Tools and Application Tuning
     Tools. Included with the SDK are Four (4) Professional NL Run Time Port
     licenses, for development purposes only.

     5.  SPEECHWORKS VOCABULARY LIBRARIES supply pre-packaged and continuously
     maintained language contexts for spoken words/phrases. The User Interface
     for the application using these libraries is not included. The following
     libraries are currently available: (i) Stock Names & Symbols Vocabulary and
     (ii) Mutual Fund Names & Symbols Vocabulary.

                                                                         Page 10
<PAGE>

                                   EXHIBIT B

                              INFRASTRUCTURE COSTS

GENERAL

     N2P and SWI will [] generated by or through the facilities services.  For
     the License Agreement, [] will only comprise that generated from [] to []
     by [  ] and [] in a [].

GROSS REVENUE

     Gross Revenue is [] in [  ] that are [] on [  ].  This definition excludes
     [] from [] that [] that are [], and do [] to []. Notwithstanding anything
     contained in this Exhibit or the Letter to which it is attached, [] that []
     and [] associated with the [] and [] and [] shall not [] to be []
     hereunder.

IDENTIFICATION OF EXPENSES

     For the purpose of this [  ] calculation, only [] with [] will be
     considered.  These [] will include:

     Network Traffic Charges
     -----------------------

            This [] includes the [] with (a) [], (b) [], and (c) [].  These []
            are [] and can [] as the following: [], [], [], [], etc.

     Recurring Provisioning and Leased-Line Costs
     --------------------------------------------

            This [] includes [] with [] a [  ] and [] or [] used [].  [] include
            the [] to [] as [] / [], [], and [].  These [] typically [] and are
            based on [], but they may also include [].  [] include the [] (such
            as []) that might be used to [].

     Fraud and Charge-backs
     ----------------------

            Net2Phone will recapture any fraudulent generated refunds or bad
            debts. Net2Phone will use reasonable care and practices to minimize
            such occurrences.

     Taxes
     -----

            To the extent Taxes are not charged to the customer, Net2Phone will
            pay such charges directly.

NET REVENUE AVAILABLE FOR SHARE BY NET2PHONE AND SWI

     [] is [] as [], as defined above.

                                                                         Page 11
<PAGE>

                                   EXHIBIT C
                        Current Time and Materials Fees

<TABLE>
<CAPTION>
                                  PER EIGHT-HOUR     MINIMUM NUMBER OF
            SERVICE                  DAY RATE              DAYS

------------------------------------------------------------------------
<S>                               <C>              <C>
 Project Management                $ 2,500                 5 days
------------------------------------------------------------------------
 Application Consulting            $ 2,000                 5 days
------------------------------------------------------------------------
 Speech Scientist                  $ 2,000                 5 days
------------------------------------------------------------------------
 Speech User Interface Design      $ 1,500                 5 days
------------------------------------------------------------------------
 Application Development           $ 1,500                 5 days
------------------------------------------------------------------------
 Systems Integration               $ 1,500                 5 days
------------------------------------------------------------------------
 Operations Support                $ 1,000                20 days
--------------------------------
------------------------------------------------------------------------
 Installation Services             $ 1,000                 5 days
------------------------------------------------------------------------
</TABLE>

                                                                         Page 12<PAGE>

                                                                     Exhibit 4.3

                                {FACE OF NOTE}

                             COMPLETEL EUROPE N.V.

                            14% Senior Note Due 2010

                                                                      (Euro)

ISIN No.

No.

          COMPLETEL EUROPE N.V., a Netherlands public company with limited
liability (incorporated with limited liability in The Netherlands and having its
statutory seat in Amsterdam), (the "Company," which term includes any successor
under the Indenture hereinafter referred to), for value received, promises to
pay to _______________, or its registered assigns, the principal sum of
Euro ((euro)                ) on April 15, 2010.

          Interest Payment Dates:  April 15 and October 15, commencing October
15, 2000.

          Reference is hereby made to the further provisions of this Note set
forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.
<PAGE>

          IN WITNESS WHEREOF, the Company has caused this Note to be signed
manually by its duly authorized signatories.

                              COMPLETEL EUROPE N.V.

                              By: ____________________________________
                                  Name:
                                  Title:

                              By: ____________________________________
                                  Name:
                                  Title:

                   (Trustee's Certificate of Authentication)

          This is one of the 14% Senior Notes due 2010 described in the within-
mentioned Indenture.

Date:

                              THE CHASE MANHATTAN BANK,

                                 as Trustee

                              By: ____________________________________
                                  Authorized Signatory
<PAGE>

                            {REVERSE SIDE OF NOTE}

                             COMPLETEL EUROPE N.V.

                            14% Senior Note due 2010

1.   Principal and Interest.
     ----------------------

          The Company will pay the principal of this Note on April 15, 2010.

          The Company promises to pay interest on the principal amount of this
Note on each Interest Payment Date, as set forth below, at the rate per annum
shown above.

          Interest will be payable semiannually (to the holders of record of the
Notes) at the close of business on April 1 or October 1 immediately preceding
the Interest Payment Date (the "Regular Record Date"), on each Interest Payment
Date, commencing October 15, 2000; provided that no interest shall accrue on the
principal amount of this Note prior to April 13, 2000.

          Interest on the Notes will accrue from the most recent date to which
interest has been paid or, if no interest has been paid, from April 13, 2000.
Interest will be computed on the basis of a 360-day year of twelve 30-day
months.

          The Company shall pay interest on overdue principal and premium, if
any, and interest on overdue installments of interest, to the extent lawful, at
a rate per annum that is the then applicable interest rate borne by the Notes.

2.   Method of Payment.
     -----------------

     The Company will pay interest (except defaulted interest) on the principal
amount of the Notes as provided above on each April 15 and October 15 to the
persons who are Holders (as reflected in the Security Register at the close of
business on the Regular Record Date), in each case, even if the Note is canceled
on registration of transfer or registration of exchange after such record date;
provided that, with respect to the payment of principal, the Company will make
payment to the Holder that surrenders this Note to a Principal Paying Agent on
or after April 15, 2010.

     The Company will pay principal, premium, Additional Amounts if any, and as
provided above, interest in euro, in same day funds, that at the time of payment
is legal tender for payment of public and private debts. However, the Company
may
<PAGE>

pay principal, premium, if any, and interest by its check payable in such money.
It may mail an interest check to a Holder's registered address (as reflected in
the Security Register). If a payment date is a date other than a Business Day at
a place of payment, payment may be made at that place on the next succeeding day
that is a Business Day and no interest shall accrue for the intervening period.

3.   Principal Paying Agent and Registrar.
     ------------------------------------

          Initially, the Trustee will act as authenticating agent, Principal
Paying Agent and Registrar in the Borough of Manhattan, The City of New York and
London, England and Banque Internationale a Luxembourg S.A. will act as
Principal Paying Agent and Registrar in Luxembourg.  The Company may change any
authenticating agent, Principal Paying Agent or Registrar without notice.  The
Company, any Subsidiary or any Affiliate of any of them may act as Principal
Paying Agent, Registrar or co-Registrar.

4.   Indenture; Limitations.
     ----------------------

          The Company issued the Notes under an Indenture dated as of April 13,
2000 (the "Indenture"), between the Company and The Chase Manhattan Bank (the
"Trustee").  Capitalized terms herein are used as defined in the Indenture
unless otherwise indicated.  The terms of the Notes include those stated in the
Indenture and those made part of the Indenture by reference to the Trust
Indenture Act.  The Notes are subject to all such terms, and Holders are
referred to the Indenture and the Trust Indenture Act for a statement of all
such terms.  To the extent permitted by applicable law, in the event of any
inconsistency between the terms of this Note and the terms of the Indenture, the
terms of the Indenture shall control.  This is one of the Notes referred to in
the Indenture.  The Initial Notes and the Exchange Notes are unsecured (except
to the limited extent provided in the Indenture and the Pledge Agreement) and
unsubordinated obligations of the Company limited in aggregate principal amount
not to exceed [_]300,000,000, as provided in the Indenture.

5.   Additional Amounts.
     ------------------

          The Company will pay to the Holders of Notes such Additional Amounts
as may become payable under Section 4.20 of the Indenture.

6.   Redemption.
     ----------

          (a)  The Notes will be redeemable, at the Company's option, in whole
or in part, at any time or from time to time, on or after April 15, 2005 and
prior to maturity, at the
<PAGE>

Redemption Prices (expressed in percentages of principal amount) set forth
below, plus accrued and unpaid interest, if any, to the Redemption Date (subject
to the right of Holders of record on the relevant Regular Record Date that is on
or prior to the Redemption Date to receive interest due on an Interest Payment
Date), if redeemed during the 12-month period commencing on April 15 of the
years set forth below:

                                                      Redemption
       Year                                              Price
       ----                                           ----------
       2005                                           107.000%
       2006                                           104.667%
       2007                                           102.333%
       2008 and thereafter                            100.000%

          (b)  In addition, at any time on or prior to April 15, 2003 the
Company may redeem up to 35% of the principal amount of the Notes originally
issued with the proceeds of one or more Public Equity Offerings following which
there is a Public Market, at the Company's option, at any time or from time to
time in part, at a Redemption Price (expressed as a percentage of principal
amount on the Redemption Date) of 114.00% plus accrued and unpaid interest, if
any, to the Redemption Date; provided that (i) at least 65% of the aggregate
principal amount of Notes remains outstanding after each such redemption and
(ii) the Company mails a notice of such redemption within 60 days of receipt of
the Public Equity Offering proceeds to be so applied.

          Notice of any optional redemption will be mailed at least 30 days but
not more than 60 days before the Redemption Date to each Holder of Notes to be
redeemed at his last address as it appears in the Security Register.  So long as
the Notes are listed on the Luxembourg Stock Exchange and the rules of such
exchange so require, notice of redemption shall be published in a daily
newspaper of general circulation in Luxembourg (which is expect to be the
Luxemberger Wort).  On and after the Redemption Date, interest ceases to accrue
on Notes or portions of Notes called for redemption, unless the Company defaults
in the payment of the Redemption Price.  The Trustee may select for redemption
portions of the principal amount of the Notes that have denominations equal to
(euro)1,000 integral multiples thereof, so long as no Holder holds Notes with
less than (euro)50,000 principal amount after such redemption.

7.   Redemption for Changes in Withholding Taxes.
     -------------------------------------------

          The Company may also have the option to redeem the Notes, in whole,
but not in part, in the event of certain changes in the tax laws such that the
Company would be required to pay Additional Amounts, subject to Section 3.01(c)
of the Indenture.
<PAGE>

8.   Repurchase upon Change in Control.
     ---------------------------------

          Upon the occurrence of an Change of Control, each Holder shall have
the right to require the repurchase of its Notes by the Company in cash pursuant
to the offer described in the Indenture at a purchase price equal to 101% of the
principal amount thereof plus accrued interest, if any, to the date of purchase
(the "Change of Control Payment").

          A notice of such Change of Control will be mailed within 30 days after
any Change of Control occurs to each Holder at his last address as it appears in
the Security Register.  On and after the Change of Control Payment Date,
interest ceases to accrue and the original issue discount ceases to accrete on
Notes or portions of Notes surrendered for purchase by the Company, unless the
Company defaults in the payment of the Change of Control Payment.

9.   Denominations; Transfer; Exchange.
     ---------------------------------

          The Notes are in registered form without coupons in denominations of
(euro)50,000 of principal amount and multiples of (euro)1,000 in excess thereof.
A Holder may register the transfer or exchange of Notes in accordance with the
Indenture. The Registrar may require a Holder, among other things, to furnish
appropriate endorsements and transfer documents and to pay any taxes and fees
required by law or permitted by the Indenture. The Registrar need not register
the transfer or exchange of any Notes selected for redemption. Also, it need not
register the transfer or exchange of any Notes for a period of 15 days before a
selection of Notes to be redeemed is made.

10.  Persons Deemed Owners.
     ---------------------

          A Holder shall be treated as the owner of a Note for all purposes.

11.  Unclaimed Money.
     ---------------

          If money for the payment of principal, premium, if any, or interest
remains unclaimed for two years, the Trustee and the Principal Paying Agent will
pay the money back to the Company at its request.  After that, Holders entitled
to the money must look to the Company for payment, unless an abandoned property
law designates another Person, and all liability of the Trustee and such
Principal Paying Agent with respect to such money shall cease.

12.  Discharge Prior to Redemption or Maturity.
     -----------------------------------------

          If the Company deposits with the Trustee money or Government
Securities sufficient to pay the then outstanding
<PAGE>

principal of, premium, if any, and accrued interest on the Notes (a) to
redemption or maturity, the Company will be discharged from this Indenture and
the Notes, except in certain circumstances for certain sections thereof, and (b)
to the Stated Maturity, the Company will be discharged from certain covenants
set forth in the Indenture.

13.  Legal Defeasance and Covenant Defeasance.
     ----------------------------------------

          The Company may be discharged from its obligations under the Indenture
and the Notes except for certain provisions thereof, and may be discharged from
obligations to comply with certain covenants contained in the Indenture and the
Notes, in each case upon satisfaction of certain conditions specified in the
Indenture.

14.  Amendment; Supplement; Waiver.
     -----------------------------

          Subject to certain exceptions, the Indenture or the Notes may be
amended or supplemented with the consent of the Holders of at least a majority
in principal amount of the Notes then outstanding, and any existing default or
compliance with any provision may be waived with the consent of the Holders of
at least a majority in principal amount of the Notes then outstanding.  Without
notice to or the consent of any Holder, the parties thereto may amend or
supplement the Indenture or the Notes to, among other things, cure any
ambiguity, defect or inconsistency and make any change that does not adversely
affect the rights of any Holder in any material respect.  Certain modifications
will require the consent of each Holder affected thereby.

15.  Restrictive Covenants.
     ---------------------

          The Indenture imposes certain limitations on the ability of the
Company and its Restricted Subsidiaries, among other things, to Incur additional
Indebtedness, make Restricted Payments, use the proceeds from Asset Sales,
engage in transactions with Affiliates or merge, consolidate or transfer
substantially all of its assets.  Within 90 days after the end of each fiscal
quarter, the Company must report to the Trustee on compliance with such
limitations.

16.  Successor Persons.
     -----------------

          When a successor person or other entity assumes all the obligations of
its predecessor under the Notes and the Indenture, the predecessor person will
be released from those obligations.
<PAGE>

17.  Defaults and Remedies.
     ---------------------

          If an Event of Default (other than an Event of Default specified in
clause (g) or (h) of Section 6.01 of the Indenture that occur with respect to
the Company) occurs and is continuing, the Trustee or the Holders of at least
25% in principal amount of the Notes may declare all the Notes to be due and
payable.  If a bankruptcy or insolvency default with respect to the Company
occurs and is continuing, the Notes automatically become due and payable.
Holders may not enforce this Indenture or the Notes except as provided in the
Indenture.  The Trustee may require indemnity satisfactory to it before it
enforces the Indenture or the Notes.  Subject to certain limitations, Holders of
at least a majority in principal amount of the Notes then outstanding may direct
the Trustee in its exercise of any trust or power.

18.  Trustee Dealings with Company.
     -----------------------------

          Subject to the Trust Indenture Act, the Trustee under the Indenture,
in its individual or any other capacity, may make loans to, accept deposits from
and perform services for the Company or its Affiliates and may otherwise deal
with the Company or its Affiliates as if it were not the Trustee.

19.  No Recourse Against Others.
     --------------------------

          No incorporator or any past, present or future partner, shareholder,
other equity holder, officer, director, manager, employee, board member or
controlling person as such, of the Company or of any successor Person shall have
any liability for any obligations of the Company under the Notes or this
Indenture or for any claim based on, in respect of or by reason of, such
obligations or their creation.  Each Holder by accepting a Note waives and
releases all such liability.  The waiver and release are part of the
consideration for the issuance of the Notes.

20.  Authentication.
     --------------

          This Note shall not be valid until the Trustee or authenticating agent
signs the certificate of authentication on the other side of this Note.

21.  Abbreviations.
     -------------

          Customary abbreviations may be used in the name of a Holder or an
assignee, such as:  TEN COM (= tenants in common), TEN ENT (= tenants by the
entireties), JT TEN (= joint tenants with right of survivorship and not as
tenants in common), CUST (= Custodian) and U/G/M/A (= Uniform Gifts to Minors
Act).
<PAGE>

          The Company will furnish to any Holder upon written request and
without charge a copy of the Indenture.  Requests may be made to CompleTel
Europe N.V., Kruisweg 609, 2132 NA Hoofddorp, The Netherlands, Attention:  Chief
Financial Officer.

22.  Choice of Law.
     -------------

          The laws of the State of New York shall govern the Indenture and this
Note without giving effect to applicable principles of conflicts of laws to the
extent that the application of the law of another jurisdiction would be required
thereby.
<PAGE>

                                ASSIGNMENT FORM

I or we assign and transfer this Note to

________________________________________________________________________________

________________________________________________________________________________
(Print or type name, address and zip code of assignee or transferee)

________________________________________________________________________________
(Insert Social Security or other identifying number of assignee or transferee)

and irrevocably appoint ________________________________________________________
agent to transfer this Security on the books of the Company.  The agent may
substitute another to act for him.

Dated:___________________  Signed: _______________________
                                         (Signed exactly as name appears on the
                                         other side of this Note)

Signature Guarantee: ___________________________________________________________
                    Participant in a recognized Signature Guarantee Medallion
                    Program (or other signature guarantor program reasonably
                    acceptable to the Trustee)
<PAGE>

                      OPTION OF HOLDER TO ELECT PURCHASE

          If you wish to have this Note purchased by the Company pursuant to
Section 4.10 or Section 4.12 of this Indenture, check the Box:  [     ]

          If you wish to have a portion of this Note purchased by the Company
pursuant to Section 4.10 or Section 4.12 of the Indenture, state the amount (in
principal amount):  [(Euro)]_________.

Date:  _________________

Your Signature:

_______________________________________________________________________________
       (Sign exactly as your name appears on the other side of this Note)

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00011-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00011-of-00352.parquet"}]]