UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549   FORM 10-K   (Mark One) ☒
ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2023. or  ☐
TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from  to
.   SANTANDER
DRIVE AUTO RECEIVABLES TRUST 2021-4 (Exact name of issuing entity as specified in its
charter) Commission file number of the issuing entity:
333-228364-18 Central Index Key Number of issuing
entity: 0001883955 SANTANDER DRIVE AUTO RECEIVABLES LLC (Exact name of depositor as specified in its charter) Commission file number of depositor: 333-228364 Central Index Key Number of depositor: 0001383094 SANTANDER CONSUMER USA INC. (Exact name of sponsor as specified in its charter)   Central Index
Key Number of sponsor: 0001540151 Delaware (State or other jurisdiction of incorporation or organization of the issuing entity) 86-6429473 (I.R.S. Employer Identification No. of the issuing entity) c/o Santander Drive Auto Receivables LLC 1601 Elm Street, Suite 800 Dallas, Texas 75201 (Address of principal executive offices) (214) 292-1930 (Telephone number, including area code) Securities Registered Pursuant to Section 12(b) of the Securities Exchange Act of 1934: None Securities Registered Pursuant to Section 12 (g) of the Securities Exchange Act of 1934: None   Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities
Act. Yes ☐ No ☒ Indicate by check mark if the registrant is not required to file reports pursuant to Section 13
or Section 15(d) of the Act. Yes ☐ No ☒ Indicate by check mark whether the registrant (1) has filed all
reports required to be filed by Section 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 90 days. Yes ☒ No ☐ Indicate by check mark whether the registrant has submitted
electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the
registrant was required to submit such files). Yes ☒ No ☐ Indicate by check mark whether the registrant is a large
accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of large accelerated filer, accelerated
filer, smaller reporting company, and emerging growth company in Rule 12b-2 of the Exchange Act.  Large accelerated filer

☐

Accelerated filer

☐Non-accelerated filer

☒

Smaller reporting company

☐Emerging growth company

☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period
for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ Indicate
by check mark whether the registrant has filed a report on and attestation to its managements assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the
Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☐ If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in
the filing reflect the correction of an error to previously issued financial statements. ☐ Indicate by check mark whether any of those error
corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrants executive officers during the relevant recovery period pursuant to §240.10D-1(b). ☐ Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes ☐ No ☒ State the aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, or the average bid and asked price of such common
equity, as of the last business day of the registrants most recently completed second fiscal quarter. Not applicable DOCUMENTS INCORPORATED BY REFERENCE List
hereunder the following documents if incorporated by reference and the Part of the Form 10-K (e.g. Part I, Part II, etc.) into which the document is incorporated: (1) Any annual report to security
holders; (2) Any proxy information statement; and (3) Any prospectus filed pursuant to Rule 424(b) or (c) under the Securities Act of 1933. The listed documents should be clearly described for identification purposes (e.g., annual
report to security holders for fiscal year ended December 24, 1980). None




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PART I The following items have been omitted in accordance with General Instruction J to Form 10-K:  Item 1
Business  Item 1A
Risk Factors  Item 1C
Cybersecurity  Item 2
Properties  Item 3
Legal Proceedings  Item 1B.
Unresolved Staff Comments Nothing to report.  Item 4.
Mine Safety Disclosures 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 (Financial Information) Nothing to report. Item 1114(b)(2) of Regulation AB. Credit Enhancement and Other Support, Except for Certain Derivatives Instruments (Information Regarding Significant
Enhancement Providers) Nothing to report. Item 1115(b) of Regulation AB. Certain Derivatives Instruments (Financial Information) Nothing to report. Item 1117 of Regulation AB. Legal
Proceedings. Nothing to report.  2




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PART II The following items have been omitted in accordance with General Instruction J to Form 10-K:  Item 5
Market for Registrants Common Equity, Related Stockholder Matters and Issuer Purchases of Equity
Securities  Item 6
[Reserved]  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.  Item 9C.
Disclosure Regarding Foreign Jurisdictions that Prevent Inspections Not applicable.  3




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PART III The following items have been omitted in accordance with General Instruction J to Form 10-K:  Item 10
Directors, Executive Officers, and Corporate Governance  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, and Director Independence  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 Related Transactions Information required by Item 1119 of Regulation AB has been omitted from this report on Form 10-K in reliance on the
Instruction to Item 1119. Item 1122 of Regulation AB. Compliance with Applicable Servicing Criteria Each of Santander Consumer USA Inc. and Citibank, N.A. (each, a Servicing Participant) have been identified by the issuing entity as parties
participating in the servicing function with respect to the pool assets held by the issuing entity. Each of the Servicing Participants has completed a report on an assessment of compliance with the servicing criteria applicable to it (each, a
Report on Assessment), which Reports on Assessment are attached as exhibits to this Form 10-K. In addition, each of the Servicing Participants has provided an attestation report (each, an
Attestation Report) by one or more registered public accounting firms, which reports are also attached as exhibits to this Form 10-K. None of the Reports on Assessment or the related Attestation Reports has identified any material instances of noncompliance with the servicing criteria
described in the related Report on Assessment as being applicable to such Servicing Participant. Item 1123 of Regulation AB. Servicer Compliance
Statements Santander Consumer USA Inc. has been identified by the issuing entity as the servicer with respect to the asset pool held by the issuing
entity. Santander Consumer USA Inc. has completed a statement of compliance with applicable servicing criteria (a Compliance Statement) signed by an authorized officer. The Compliance Statement is attached as an exhibit to this Form 10-K.  4




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PART IV  Item 15.
Exhibit and Financial Statement Schedules  (a)(1)

Not  Applicable.(a)(2)

Not Applicable.(a)(3)

See Item 15(b) below.(b)

Exhibits The exhibits listed below are either included or incorporated by reference as indicated:  Exhibit No.

Description1.1

Underwriting Agreement, dated as of October 
19, 2021, among Santander Drive Auto Receivables LLC (Santander Drive), Santander Consumer USA Inc. (SC) and Citigroup Global Markets Inc., as representative of the several underwriters (incorporated by reference to Exhibit 1.1 of
 Form 8-K filed by the Issuer (Commission File No. 333-228364-18) with the Securities and Exchange Commission on
October 21, 2021)3.1

Amended and Restated Limited Liability Company Agreement of Santander Drive dated as of March 
7, 2007 (incorporated by reference to Exhibit 3.1 of Form SF-3 filed by Santander Drive (Commission File No. 
333-228364) with the Securities and Exchange Commission on November 13, 2018)3.2

First Amendment to Amended and Restated Limited Liability Company Agreement, dated as of February 
28, 2017, by SC, as sole equity member (incorporated by reference to Exhibit 3.2 of Form SF-3 filed by Santander Drive (Commission File No. 
333-228364) with the Securities and Exchange Commission on November 13, 2018)4.1

Indenture, dated as of October 
27, 2021, between Santander Drive Auto Receivables Trust 2021-4, as issuer (the Issuer), and Citibank, N.A., as indenture trustee (the Indenture Trustee) (incorporated by reference to Exhibit
 4.1 of Form 8-K filed by the Issuer (Commission File No. 333-228364-18) with the Securities and Exchange Commission on
October 27, 2021)10.1

Purchase Agreement, dated as of October 27, 2021, between SC and Santander Drive (incorporated by reference to Exhibit 10.1 of Form 8-K filed by the Issuer (Commission File No. 333-228364-18) with the Securities and Exchange Commission on October 27, 2021)10.2

Sale and Servicing Agreement, dated as of October 
27, 2021, among the Issuer, Santander Drive, SC and the Indenture Trustee (incorporated by reference to Exhibit 10.2 of Form 8-K filed by the Issuer (Commission File No. 333-228364-18) with the Securities and Exchange Commission on October 27, 2021)10.3

Administration Agreement, dated as of October 
27, 2021, among the Issuer, SC, as administrator, and the Indenture Trustee (incorporated by reference to Exhibit 10.3 of Form 8-K filed by the Issuer (Commission File No. 333-228364-18) with the Securities and Exchange Commission October 27, 2021)10.4

Amended and Restated Trust Agreement, dated as of October 
27, 2021, between Santander Drive and Wilmington Trust, National Association, not in its individual capacity but solely as owner trustee for the Issuer (incorporated by reference to Exhibit 10.4 of Form 8-K filed
 by the Issuer (Commission File No. 333-228364-18) with the Securities and Exchange Commission on October 27, 2021)  5




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10.5

Asset Representations Review Agreement, dated as of October 
27, 2021, among the Issuer, SC, as sponsor and servicer, and Clayton Fixed Income Services, LLC, as asset representations reviewer (incorporated by reference to Exhibit 10.5 of Form 8-K filed by the Issuer (Commission
 File No. 333-228364-18) with the Securities and Exchange Commission on October 27, 2021)31.1

Certification (Santander Drive)33.1

Managements Assessment of Compliance with SEC Regulation AB Servicing Criteria (SC)33.2

Assessment of Compliance with the Applicable Servicing Criteria (Citibank, N.A.)34.1

Report of Independent Registered Public Accounting Firm (PricewaterhouseCoopers LLP with respect to SC)34.2

Report of Independent Registered Public Accounting Firm (KPMG LLP with respect to Citibank, N.A.)35.1

Servicer Compliance Statement (SC)  (c)
Not Applicable.  Item 16.
Form 10-K Summary None. Supplemental information to be Furnished With Reports
Filed Pursuant to Section 15(d) of the Act by Registrants Which Have Not Registered Securities Pursuant to Section 12 of the Act No annual
report, proxy statement, form of proxy or other proxy soliciting material has been sent to certificateholders, and the registrant does not presently contemplate sending any such materials subsequent to the filing of this report.  6




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SIGNATURES Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to
be signed on its behalf by the undersigned, thereunto duly authorized. Date: March 29, 2024  SANTANDER DRIVE AUTO RECEIVABLES LLC, as depositorBy:

/s/ Corey HenryName:

Corey HenryTitle:

President and Chief Executive Officer(senior officer in charge of securitization of the depositor)
  7