# EDGAR Filing Document

**Accession Number:** 0001275214
**File Stem:** 0000945621-23-000116
**Filing Date:** 2023-2
**Character Count:** 16646
**Document Hash:** 1870b25db3a90ff4cc2307fb25518ae2
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000945621-23-000116.hdr.sgml**: 20230228

**ACCESSION NUMBER**: 0000945621-23-000116

**CONFORMED SUBMISSION TYPE**: SC 13G/A

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20230228

**DATE AS OF CHANGE**: 20230228

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** CALAMOS STRATEGIC TOTAL RETURN FUND
- **CENTRAL INDEX KEY:** 0001275214
- **IRS NUMBER:** 043785941
- **FISCAL YEAR END:** 1031

**FILING VALUES:**
- **FORM TYPE:** SC 13G/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-84333
- **FILM NUMBER:** 23680302

**BUSINESS ADDRESS:**
- **STREET 1:** 2020 CALAMOS COURT
- **STREET 2:** C/O CALAMOS ADVISORS LLC
- **CITY:** NAPERVILLE
- **STATE:** IL
- **ZIP:** 60653
- **BUSINESS PHONE:** 6302451046

**MAIL ADDRESS:**
- **STREET 1:** 2020 CALAMOS COURT
- **STREET 2:** C/O CALAMOS ADVISORS LLC
- **CITY:** NAPERVILLE
- **STATE:** IL
- **ZIP:** 60653
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Sun Life Assurance Co of Canada
- **CENTRAL INDEX KEY:** 0001381352
- **IRS NUMBER:** 381082080
- **STATE OF INCORPORATION:** A6
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SC 13G/A

**BUSINESS ADDRESS:**
- **STREET 1:** ONE YORK STREET
- **CITY:** TORONTO
- **STATE:** A6
- **ZIP:** M5J 0B6
- **BUSINESS PHONE:** 416-979-9966

**MAIL ADDRESS:**
- **STREET 1:** ONE YORK STREET
- **CITY:** TORONTO
- **STATE:** A6
- **ZIP:** M5J 0B6

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Sun Life Assurance CO of Canada
- **DATE OF NAME CHANGE:** 20061117

&nbsp;&nbsp;&nbsp;&nbsp;<br>

#### UNITED STATES

#### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

#### SCHEDULE 13G

#### Under the Securities Exchange Act of 1934

#### (Amendment No. 5)\*

---

| |
|:---|
| CALAMOS STRATEGIC TOTAL RETURN FUND<br>|
| (Name of Issuer) |
| Series B Mandatory Redeemable Preferred Shares<br>Series C Mandatory Redeemable Preferred Shares<br>|
| (Title of Class of Securities) |
| 128125\*37<br>128125\*45<br>|
| (CUSIP Number) |
| December 31, 2022 |
| (Date of Event which Requires Filing of this Statement) |

---

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

☑&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Rule 13d-1(b)

☐&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Rule 13d-1(c)

☐&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Rule 13d-1(d)

\*The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

------

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| | | |
|:---|:---|:---|
| **1** | NAMES OF REPORTING PERSON | NAMES OF REPORTING PERSON |
| **1** | Sun Life Assurance Company of Canada | Sun Life Assurance Company of Canada |
| **1** | Sun Life Assurance Company of Canada | Sun Life Assurance Company of Canada |
| **2** | CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP | CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP |
| **2** | (a)☐ | (a)☐ |
| **2** | (b)☐ | (b)☐ |
| **3** | SEC USE ONLY | SEC USE ONLY |
| **3** |  |  |
| **3** |  |  |
| **4** | **CITIZENSHIP OR PLACE OF ORGANIZATION** | **CITIZENSHIP OR PLACE OF ORGANIZATION** |
| **4** | Canada | Canada |
| **4** | Canada | Canada |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **5** | SOLE VOTING POWER |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **5** | 720000 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **5** | 720000 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **6** | SHARED VOTING POWER |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **6** | 0 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **6** | 0 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **7** | SOLE DISPOSITIVE POWER |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **7** | 720000 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **7** | 720000 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **8** | SHARED DISPOSITIVE POWER |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **8** | 0 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **8** | 0 |
| **9** | AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON | AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON |
| **9** | 720000 | 720000 |
| **9** | 720000 | 720000 |
| **10** | **CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES**  | **CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES**  |
| **10** | ☐ | ☐ |
| **10** | ☐ | ☐ |
| **11** | PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) | PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) |
| **11** | 5.56% | 5.56% |
| **11** | 5.56% | 5.56% |
| **12** | TYPE OF REPORTING PERSON | TYPE OF REPORTING PERSON |
| **12** | FI, IC, CO | FI, IC, CO |
| **12** | FI, IC, CO | FI, IC, CO |

---

------

---

| | | |
|:---|:---|:---|
| **1** | NAMES OF REPORTING PERSON | NAMES OF REPORTING PERSON |
| **1** | Sun Life Financial Inc. | Sun Life Financial Inc. |
| **1** | Sun Life Financial Inc. | Sun Life Financial Inc. |
| **2** | CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP | CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP |
| **2** | (a)☐ | (a)☐ |
| **2** | (b)☐ | (b)☐ |
| **3** | SEC USE ONLY | SEC USE ONLY |
| **3** |  |  |
| **3** |  |  |
| **4** | **CITIZENSHIP OR PLACE OF ORGANIZATION** | **CITIZENSHIP OR PLACE OF ORGANIZATION** |
| **4** | Canada | Canada |
| **4** | Canada | Canada |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **5** | SOLE VOTING POWER |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **5** | 0 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **5** | 0 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **6** | **SHARED VOTING POWER** |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **6** | 720000 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **6** | 720000 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **7** | **SOLE DISPOSITIVE POWER** |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **7** | 0 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **7** | 0 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **8** | SHARED DISPOSITIVE POWER |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **8** | 720000 |
| **NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH** | **8** | 720000 |
| **9** | AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON | AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON |
| **9** | 720000 | 720000 |
| **9** | 720000 | 720000 |
| **10** | CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES | CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES |
| **10** | ☐ | ☐ |
| **10** | ☐ | ☐ |
| **11** | PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) | PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) |
| **11** | 5.56% | 5.56% |
| **11** | 5.56% | 5.56% |
| **12** | **TYPE OF REPORTING PERSON** | **TYPE OF REPORTING PERSON** |
| **12** | FI, HC, CO | FI, HC, CO |
| **12** | FI, HC, CO | FI, HC, CO |

---

&nbsp;&nbsp;&nbsp;&nbsp;<br>

------

---

| | |
|:---|:---|
| **Item 1.**<br>(a) | **Name of Issuer:** |
|  | Calamos Strategic Total Return Fund |
| (b) | **Address of Issuer's Principal Executive Offices:** |
|  | 2020 Calamos Court<br>Naperville, Illinois 60563 |
| **Item 2.**<br> (a)<br> **** <br>(i)<br>(ii)<br>| **Name of Persons Filing:**<br> **** <br>**Sun Life Assurance Company of Canada ("SLA")**<br>**Sun Life Financial Inc. ("SLF")** |
| (b) | **Address of Principal Business Office or, if none, Residence :** |
|  | SLA and SLF:<br>One York Street<br>Toronto, Ontario, Canada M5J 0B6 |
| (c) | **Citizenship or Place of Organization:** |
|  | SLA and SLF: Canada |
| (d) | **Title of Class of Securities:** |
|  | <br> Mandatory Redeemable Preferred Shares |
| (e) | **CUSIP Number:**<br>128125\*37<br>128125\*45 |

---

---

| | |
|:---|:---|
| **Item 3.** | **If this statement is filed pursuant to Sections 240.13d-1(b) or 240.13d-2(b) or (c),**<br> **check whether the person filing is a:** |
| (a) | [ ] Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);<br>|
| (b) | [ ] Bank as defined in Section 3(a)(6) of the Act (15 U.S.C. 78c);<br>|
| (c) | [ ] Insurance company as defined in Section 3(a)(19) of the Act (15 U.S.C. 78c);<br>|
| (d) | [ ] Investment company registered under Section 8 of the Investment<br> &nbsp;&nbsp;&nbsp;&nbsp; Company Act of 1940 (U.S.C. 80a-8);<br>|
| (e) | [ ] An investment adviser in accordance with Section<br> &nbsp;&nbsp;&nbsp;&nbsp; 240.13d-1(b)(1)(ii)(E); |
| (f) | [ ] An employee benefit plan or endowment fund in accordance with<br> &nbsp;&nbsp;&nbsp;&nbsp; Section 240.13d-1(b)(1)(ii)(F); |
| (g) | [X] A parent holding company or control person in accordance with<br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Section 240.13d-1(b)(1)(ii)(G); |
| (h) | [ ] A savings associations as defined in Section 3(b) of the Federal<br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Deposit Insurance Act (12 U.S.C. 1813);<br>|
| (i) | [ ] A church plan that is excluded from the definition of an investment<br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; company under Section 3(c)(14) of the Investment Company Act<br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; of 1940 (15 U.S.C. 80a-3);<br>|

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| | |
|:---|:---|
| (j) | [X ] A non-U.S. institution in accordance with Section 240.13d-1(b)(1) (ii)(J). |
| (k) | [ ] Group, in accordance with Section 240.13d-1(b)(1)(ii)(K). |
| If filing as a non-U.S. institution in accordance with Section 240.13d-1(b)(1)(ii)(J), please specify the type of institution: Insurance Company | If filing as a non-U.S. institution in accordance with Section 240.13d-1(b)(1)(ii)(J), please specify the type of institution: Insurance Company |

---

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| | |
|:---|:---|
| **Item 4. Ownership:** |  |
|  | Provide the following information regarding the aggregate number and percentage of the class of securities of the Issuer identified in Item 1.  |
| (a) | Amount beneficially owned: |
|  | <br> (i) SLA: 720,000<br> (ii) SLF: 720,000<br>|
| (b) | Percent of class: |
|  | <br> (i) SLA: 5.56%<br>(ii) SLF: 5.56%<br>|
| (c) | Number of shares as to which the person has: |
|  | (i)&nbsp;&nbsp;&nbsp;&nbsp; Sole power to vote or to direct the vote: |
|  | <br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (1) SLA: 720,000<br> (2) SLF: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0<br>|
|  | (ii)&nbsp;&nbsp;&nbsp;&nbsp; Shared power to vote or direct the vote: |
|  | <br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (1) SLA: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0<br> (2) SLF: 720,000<br>|
|  | (iii) Sole power to dispose or direct the disposition of: |
|  | <br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(1) SLA: 720,000<br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(2) SLF: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0 |
|  | (iv) Shared power to dispose or to direct the disposition of: |
|  | <br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(1) SLA: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 0<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(2) SLF: 720,000<br>|

---

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| | |
|:---|:---|
| **Item 5.** | **Ownership of Five Percent or Less of a Class:** |
|  | Not Applicable  |
| **Item 6.** | **Ownership of More than Five Percent on Behalf of Another Person:** |
|  | Not Applicable |

---

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| | |
|:---|:---|
| **Item 7.** | **Identification and Classification of the Subsidiary which Acquired the Security Being Reported on by the Parent Holding Company:** |
|  | Not Applicable  |
| **Item 8.** | **Identification and Classification of Members of the Group:** |
|  | Not Applicable |
| **Item 9.** | **Notice of Dissolution of Group.** |
|  | Not Applicable  |
| **Item 10.** | **Certification:** |
|  | By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.<br>By signing below I certify that, to the best of my knowledge and belief, the foreign regulatory scheme applicable to insurance companies in Canada is substantially comparable to the regulatory scheme applicable to the functionally equivalent U.S. institutions. I also undertake to furnish the Commission staff, upon request, information that would otherwise be disclosed in a Schedule 13D. |

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#### SIGNATURES

#### <br>
**The undersigned certify, after reasonable inquiry and to the best knowledge and belief of the undersigned, that the information set forth in this Statement is true, complete and correct. The undersigned agree to the filing of this single Statement on Schedule 13G in accordance with Rule 13d-1(k)(1).**

**---

| | | |
|:---|:---|:---|
|  | **Sun Life Assurance Company of Canada** | **Sun Life Assurance Company of Canada** |
| Date: February 28, 2023<br>| By:  | <u>/s/ Randolph B. Brown</u> |
|  | Name: | Randolph B. Brown |
|  | Title:  | Authorized Signatory |
|  | By:  | <u>/s/ Brett W. Pacific</u> |
| Date: February 28, 2023 | Name: | Brett W. Pacific |
|  | Title: | Authorized Signatory |
|  | Sun Life Financial Inc.  | Sun Life Financial Inc.  |
| Date: February 28, 2023  | By:  | <u>/s/ Randolph B. Brown</u> |
|  | Name:  | Randolph B. Brown  |
|  | Title: | Authorized Signatory |
| Date: February 28, 2023 | By: | <u>/s/ Brett W. Pacific</u>  |
|  | Name: | Brett W. Pacific  |
|  | Title:  | Authorized Signatory  |

---

** <br>

------

#### EXHIBIT 1
**WHEREAS**, in accordance with Rule 13d-1(k)(1) under the Securities and Exchange Act of 1934 (the "Act"), only one joint Statement and any amendments thereto need to be filed whenever one or more persons are required to file such a Statement or any amendments thereto pursuant to Section 13(d) of the Act with respect to the same securities, provided that said persons agree in writing that such Statement or amendments thereto is filed on behalf of each of them;

**NOW, THEREFORE**, the parties hereto agree as follows:

Sun Life Assurance Company of Canada and Sun Life Financial Inc. do hereby agree, in accordance with Rule 13d-1(k)(1) under the Act, to file a Statement on Schedule 13G relating to their ownership of the securities of the Issuer, and do hereby further agree that said Statement on Schedule 13G shall be filed on behalf of each of them.

#### <br>

**---

| | | |
|:---|:---|:---|
|  | **Sun Life Assurance Company of Canada** | **Sun Life Assurance Company of Canada** |
| Date: February 28, 2023<br>| By:  | <u>/s/ Randolph B. Brown</u> |
|  | Name: | Randolph B. Brown |
|  | Title:  | Authorized Signatory |
|  | By:  | <u>/s/ Brett W. Pacific</u>  |
| Date: February 28, 2023 | Name: | Brett W. Pacific |
|  | Title: | Authorized Signatory |
|  | Sun Life Financial Inc.  | Sun Life Financial Inc.  |
| Date: February 28, 2023  | By:  | <u>/s/ Randolph B. Brown</u> |
|  | Name:  | Randolph B. Brown  |
|  | Title: | Authorized Signatory |
| Date: February 28, 2023 | By: | <u>/s/ Brett W. Pacific</u> |
|  | Name: | Brett W. Pacific  |
|  | Title:  | Authorized Signatory  |

---

** <br>

<br>