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**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**Washington, D.C. 20549**

 

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**FORM 10-K**

 

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**(Mark One)**
| **x** | **ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934** |
|-------|------------------------------------------------------------------------------------------|

**For the fiscal year ended: December 31, 2006**

**or**

 
| ** ̈** | **TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934** |
|-----------|----------------------------------------------------------------------------------------------|

**For Transition period                    **

** **
| **Commission File Number of issuing entity:  333-130795-10**

**WaMu Mortgage Pass-Through Certificates, Series 2006-AR4** |
|---------------------------------------------------------------------------------------------------------------------------------|

**Commission File Number of depositor: 333-130795**

 

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**WAMU ASSET ACCEPTANCE CORP.**

**(Exact name of depositor as specified in its charter)**

  

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**WASHINGTON MUTUAL BANK**

**(Exact name of sponsor as specified in its charter)** 

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|   |                                                                                          |
|--------|-----------------------------------------------------------------------------------------------|
|   | **Delaware**                                                                                  |
|   | **(State or other jurisdiction of Incorporation**

**or organization of the issuing entity)** |
|   |
|   | **1301 Second Avenue, WMC 3501A Seattle, Washington  98101**                             |
|   | **(Address of principal executive offices**

**of issuing entity)**                           |
|   |
|   | **(206) 500-4418**                                                                            |
|   | **(Telephone number, including area code)**                                                   |
|   |
|   | 54-2195752                                                                                    |
|   | **(I.R.S. Employer Identification No.)**                                                      |
|   |
|   | **N/A**                                                                                       |
|   | **(Former name, former address, if changed since last report)**                               |

 

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Securities registered pursuant to Section 12(b) of the Act: None

Securities Registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of theSecurities Act.    Yes   ̈    No  x

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 orSection 15(d) of the Act.    Yes   ̈    No  x

Indicate by check mark whether the registrant (1) has filed all reports required to be filed bySection 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90days.    x  Yes     ̈  No

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is notcontained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part II of the Form 10-K or any amendment to this form 10-K.     ̈  [Item 405 of Regulation S-K is not applicable.]

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or anon-accelerated filer. See definition of “accelerated filer and large accelerated filer” in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer   ̈    Accelerated filer   ̈    Non-accelerated filer  x

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of theAct).    Yes   ̈    No  x

Registrant has no voting or non-voting common equity outstanding held bynon-affiliates.

 

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**PART I**

**The following Items have been omitted in accordance with General Instruction J to Form10–K:**

 

|          |         |                                                 |
|---------------|--------------|------------------------------------------------------|
| Item 1:  |    | Business.                                            |
| Item 1A: |    | Risk Factors.                                        |
| Item 2:       |    | Properties.                                          |
| Item 3:       |    | Legal Proceedings.                                   |
| Item 4:       |    | Submission of Matters to a Vote of Security Holders. |

**Item 1B. Unresolved Staff Comments.**

Not Applicable.

**Substitute information provided in accordance with General Instruction J to Form 10–K:**

 

**Item 1112(b) of Regulation AB. Significant Obligors of Pool Assets (FinancialInformation). **

 

No single obligor represents more than 10% of the pool assets held by the WaMu Mortgage Pass-ThroughCertificates, Series 2006-AR4 (the “Trust”).

**Item 1114(b)(2) of Regulation AB: Credit Enhancement and Other Support, Except for Certain DerivativesInstruments (Information Regarding Significant Enhancement Providers: Financial Information). **

No entity or group of affiliated entities that provides (1) any external credit enhancement designed to ensurethat the asset-backed securities or pool assets will pay in accordance with their terms, (2) any mechanisms to ensure that payments on the asset-backed securities are timely or (3) any derivatives whose primary purpose is to provide credit enhancement related to poolassets or the asset-backed securities is either liable or contingently liable to provide payments representing 10% or more of the cash flow supporting any offered class of asset-backed securities of the Trust.

**Item 1115(b) of Regulation AB: Certain Derivatives Instruments (FinancialInformation). **

The “aggregate significance percentage” (as defined in Item 1115 of Regulation AB) related to anyentity or group of affiliated entities providing derivative instruments that are used to alter the payment characteristics of the cashflows from the Trust and whose primary purpose is not to provide credit enhancement related to the pool assets or the asset-backedsecurities of the Trust does not equal or exceed 10%. 

**Item 1117 of Regulation AB: Legal Proceedings. **

None. 

 

**PART II**

**The following Items have been omitted in accordance with General Instruction J to Form10–K:**

 

|          |   |                                                                                                                |
|---------------|--------|---------------------------------------------------------------------------------------------------------------------|
| Item 5:  |   | Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities. |
| Item 6:  |   | Selected Financial Data.                                                                                            |
| Item 7:  |   | Management’s Discussion and Analysis of Financial Condition and Results of Operations.                        |
| Item 7A: |   | Quantitative and Qualitative Disclosures about Market Risk.                                                         |
| Item 8:  |   | Financial Statements and Supplementary Data.                                                                        |
| Item 9:  |   | Changes in and Disagreements with Accountants on Accounting and Financial Disclosure.                               |
| Item 9A: |   | Controls and Procedures.                                                                                            |

 

**Item 9B: Other Information.**

None.

**PART III**

**The following Items have been omitted in accordance with General Instruction J to Form10–K:**

 

|          |   |                                                                                            |
|---------------|--------|-------------------------------------------------------------------------------------------------|
| Item 10: |   | Directors and Executive Officers of the Registrant.                                             |
| Item 11:      |   | Executive Compensation.                                                                         |
| Item 12:      |   | Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters. |
| Item 13:      |   | Certain Relationships and Related Transactions.                                                 |
| Item 14:      |   | Principal Accountant Fees and Services.                                                         |

**Substitute information provided in accordance with General Instruction J to Form 10–K:**

 

**Item 1119 of Regulation AB: Affiliations and Certain Relationships and RelatedTransactions***.*

Pursuant to the Instructions to Item 1119 of Regulation AB, information required by Item 1119 has been omittedfrom this annual report on Form 10-K because it is substantially the same information as has been provided previously in a prospectus timely filed pursuant to Rule 424 of the General Rules and Regulations Promulgated under the Securities Act of 1933 under the sameCentral Index Key (CIK) as this annual report on Form 10-K.

**Item 1122 of Regulation AB: Compliance with Applicable Servicing Criteria.**

WaMu Asset Acceptance Corp. (in its role as depositor), Washington Mutual Bank (in its role as servicer),Washington Mutual Mortgage Securities Corp. (in its role as calculation agent) (“WMMSC”), Washington Mutual Bank fsb (in its role as custodian), and American Security Insurance Company and Standard Guaranty Insurance Company (in the role as hazardinsurance servicer) (collectively, the “Servicing Parties”) have each been identified by the registrant as parties participating in the servicing function with respect to the asset pool held by the Trust. Each of the Servicing Parties has completed areport on assessment of compliance with the servicing criteria applicable to it (each a “Servicing Report”), which Servicing Reports are attached as exhibits to this Form 10-K.  Each of the Servicing Parties have provided an attestation report (eachan “Attestation Report”) by one or more public accounting firms, which reports are also attached as exhibits to this Form 10-K.  None of the Servicing Reports or Attestation Reports has identified any material instance of noncompliance with theservicing criteria as applicable to the respective Servicing Party, except that, with respect to WMMSC and its compliance with Item 1122 (d)(2)(vii)(B), two of twelve bank statement reconciliations examined were not prepared within 30 calendar days after the bankstatement cutoff date, but were prepared within 30 calendar days after month end, which was 32 calendar days after the bank statement cutoff date.

 

**Item 1123 of Regulation AB: Servicer Compliance Statement.**

** **

Washington Mutual Bank (in its role as servicer) and WMMSC (in its role as calculation agent) have been identified by the registrant as servicers with respect to the asset pool held by the Trust.  Eachof  Washington Mutual Bank and  WMMSC has completed a statement of compliance with applicable servicing criteria (each a “Compliance Statement”), in each case signed by an authorized officer of Washington Mutual Bank and WMMSC, respectively. TheCompliance Statements are attached as exhibits to this Form 10-K.** ** None of the Compliance Statements has identified any material instance of noncompliance with the respective servicer’s obligation under the applicable servicing agreement, exceptthat WMMSC reported the following:

Funds received as prepayment fees were initially distributed on the May 2006 distribution date only to the holders of the Class PPP Certificates.  It was determined shortly thereafter, however, that aportion of such prepayment fees was due to the holders of the Class 2X Certificates.  The Trustee was promptly notified to effect the corrected distribution and an amendment to the applicable Form 10-D with a revised distribution report was filed with theSecurities and Exchange Commission and made available to investors in June 2006.

 

**PART IV**

**Item 15. Exhibits, Financial Statement Schedules.**

 
|   | (a)(1) | Not Applicable. |
|--------|--------|-----------------|

 
|   | (a)(2) | Not Applicable. |
|--------|--------|-----------------|

 
|   | (a)(3) | Not Applicable. |
|--------|--------|-----------------|

 
|   | (b) | Exhibits |
|--------|-----|----------|

 

 
| **Exhibit No.** | **  Exhibit Description**                                                                                                                                                                                                      |
|-----------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|            |                                                                                                                                                                                                                                |
| 4.1             | Pooling and Servicing Agreement (incorporated herein by reference from Exhibit 4.1 to the Form 8-K filed by the issuing entity on May 10, 2006).                                                                                    |
| 4.2             | Mortgage Loan Purchase Agreement (incorporated herein by reference from Exhibit 4.6 to the Form 8-K filed by WaMu Asset Acceptance Corp. on November 8, 2005 with respect to RegistrationStatement No. 333-123034).                 |
| 4.3             | Amended and Restated Administrative Agent Agreement (incorporated herein by reference from Exhibit 4.9 to the Form 8-K filed by WaMu Asset Acceptance Corp. on March 6, 2006 with respect toRegistration Statement No. 333-130795). |
| 31              | Certification of Thomas G. Lehmann pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                                                                                       |
| 33.1            | Report on Assessment of Compliance with Servicing Criteria for WaMu Asset Acceptance Corp.                                                                                                                                          |
| 33.2            | Report on Assessment of Compliance with Servicing Criteria for Washington Mutual Bank.                                                                                                                                              |
| 33.3            | Report on Assessment of Compliance with Servicing Criteria for Washington Mutual Mortgage Securities Corp.                                                                                                                          |
| 33.4            | Report on Assessment of Compliance with Servicing Criteria for Washington Mutual Bank fsb.                                                                                                                                          |
| 33.5            | Report on Assessment of Compliance with Servicing Criteria for American Security Insurance Company and Standard Guaranty Insurance Company.                                                                                         |
| 34.1            | Attestation Report of Deloitte & Touche LLP on Assessment of Compliance with Servicing Criteria for WaMu Asset Acceptance Corp.                                                                                                 |
| 34.2            | Attestation Report of Deloitte & Touche LLP on Assessment of Compliance with Servicing Criteria for Washington Mutual Bank.                                                                                                     |
| 34.3            | Attestation Report of Deloitte & Touche LLP on Assessment of Compliance with Servicing Criteria for Washington Mutual Mortgage Securities Corp.                                                                                 |
| 34.4            | Attestation Report of Deloitte & Touche LLP on Assessment of Compliance with Servicing Criteria for Washington Mutual Bank fsb.                                                                                                 |
| 34.5            | Attestation Report of PriceWaterhouseCoopers on Assessment of Compliance with Servicing Criteria for American Security Insurance Company and Standard Guaranty Insurance Company.                                                   |
| 35.1            | Servicer Compliance Statement of Washington Mutual Bank.                                                                                                                                                                            |
| 35.2            | Servicer Compliance Statement of Washington Mutual Mortgage Securities Corp.                                                                                                                                                        |
| 99.1            | Excerpt from Section 2 of the Term Sheet (incorporated herein by reference from Exhibit 99.1 to the Form 8-K filed by the issuing entity on May 10, 2006).                                                                          |

 

 

 

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**SIGNATURES**

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registranthas duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

 

 

|                            |   |                 |   |                        |
|---------------------------------|--------|----------------------|--------|-----------------------------|
| **WAMU ASSET ACCEPTANCE CORP.** |
|                            |   |
|                            |   |                 |
|                            |   | By:                  |   |  /s/ Thomas G. Lehmann |
|                            |   | Name:                |   |  Thomas G. Lehmann     |
|                            |   | Title:               |   |   President            |
|                            |   |
|                            |   | Date: March 15, 2007 |

 

 

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EXHIBIT INDEX

 

 
| **Exhibit No.** | **  Exhibit Description**                                                                                                                                                                                                      |
|-----------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|            |                                                                                                                                                                                                                                |
| 4.1             | Pooling and Servicing Agreement (incorporated herein by reference from Exhibit 4.1 to the Form 8-K filed by the issuing entity on May 10, 2006).                                                                                    |
| 4.2             | Mortgage Loan Purchase Agreement (incorporated herein by reference from Exhibit 4.6 to the Form 8-K filed by WaMu Asset Acceptance Corp. on November 8, 2005 with respect to RegistrationStatement No. 333-123034).                 |
| 4.3             | Amended and Restated Administrative Agent Agreement (incorporated herein by reference from Exhibit 4.9 to the Form 8-K filed by WaMu Asset Acceptance Corp. on March 6, 2006 with respect toRegistration Statement No. 333-130795). |
| 31              | Certification of Thomas G. Lehmann pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                                                                                       |
| 33.1            | Report on Assessment of Compliance with Servicing Criteria for WaMu Asset Acceptance Corp.                                                                                                                                          |
| 33.2            | Report on Assessment of Compliance with Servicing Criteria for Washington Mutual Bank.                                                                                                                                              |
| 33.3            | Report on Assessment of Compliance with Servicing Criteria for Washington Mutual Mortgage Securities Corp.                                                                                                                          |
| 33.4            | Report on Assessment of Compliance with Servicing Criteria for Washington Mutual Bank fsb.                                                                                                                                          |
| 33.5            | Report on Assessment of Compliance with Servicing Criteria for American Security Insurance Company and Standard Guaranty Insurance Company.                                                                                         |
| 34.1            | Attestation Report of Deloitte & Touche LLP on Assessment of Compliance with Servicing Criteria for WaMu Asset Acceptance Corp.                                                                                                 |
| 34.2            | Attestation Report of Deloitte & Touche LLP on Assessment of Compliance with Servicing Criteria for Washington Mutual Bank.                                                                                                     |
| 34.3            | Attestation Report of Deloitte & Touche LLP on Assessment of Compliance with Servicing Criteria for Washington Mutual Mortgage Securities Corp.                                                                                 |
| 34.4            | Attestation Report of Deloitte & Touche LLP on Assessment of Compliance with Servicing Criteria for Washington Mutual Bank fsb.                                                                                                 |
| 34.5            | Attestation Report of PriceWaterhouseCoopers on Assessment of Compliance with Servicing Criteria for American Security Insurance Company and Standard Guaranty Insurance Company.                                                   |
| 35.1            | Servicer Compliance Statement of Washington Mutual Bank.                                                                                                                                                                            |
| 35.2            | Servicer Compliance Statement of Washington Mutual Mortgage Securities Corp.                                                                                                                                                        |
| 99.1            | Excerpt from Section 2 of the Term Sheet (incorporated herein by reference from Exhibit 99.1 to the Form 8-K filed by the issuing entity on May 10, 2006).                                                                          |