Exhibit 99.1

MONTHLY SERVICER'S CERTIFICATE

CARMAX BUSINESS SERVICES, LLC

CARMAX AUTO OWNER TRUST

SERIES 2021-3

Collection Period

12/01/24-12/31/24

Determination Date

1/9/2025

Distribution Date

1/15/2025

Additional information, including defined terms, can be found in the prospectus on the SEC's EDGAR system (http://www.sec.gov) under File No. 333-228379-11.


Pool Balance
1.	Pool Balance on the close of the last day of the preceding Collection Period			$	332,722,596.89
2.	Collections allocable to Principal			$	17,384,508.99
3.	Purchase Amount allocable to Principal			$	0.00
4.	Defaulted Receivables			$	630,176.75
5.	Pool Balance on the close of the last day of the related Collection Period			$	314,707,911.15
	(Ln1 - Ln2 - Ln3 - Ln4)
6.	Total number of Receivables outstanding on the close of the last day of the related Collection Period			40,641
7.	Initial Pool Balance			$	1,754,385,994.70
		Beginning of Period		End of Period
8.	Note Balances
	a. Class A-1 Note Balance	$	0.00	$	0.00
	b. Class A-2a Note Balance	$	0.00	$	0.00
	c. Class A-2b Floating Rate Note Balance	$	0.00	$	0.00
	d. Class A-3 Note Balance	$	87,676,631.90	$	69,661,946.16
	e. Class A-4 Note Balance	$	143,290,000.00	$	143,290,000.00
	f. Class B Note Balance	$	27,190,000.00	$	27,190,000.00
	g. Class C Note Balance	$	47,370,000.00	$	47,370,000.00
	h. Class D Note Balance	$	22,810,000.00	$	22,810,000.00
	i. Note Balance (sum a - h)	$	328,336,631.90	$	310,321,946.16
9.	Pool Factors
	a. Class A-1 Note Pool Factor	0.0000000		0.0000000
	b. Class A-2a Note Pool Factor	0.0000000		0.0000000
	c. Class A-2b Floating Rate Note Pool Factor	0.0000000		0.0000000
	d. Class A-3 Note Pool Factor	0.1445211		0.1148268
	e. Class A-4 Note Pool Factor	1.0000000		1.0000000
	f. Class B Note Pool Factor	1.0000000		1.0000000
	g. Class C Note Pool Factor	1.0000000		1.0000000
	h. Class D Note Pool Factor	1.0000000		1.0000000
	i. Note Pool Factor	0.1876209		0.1773268
10.	Overcollateralization Target Amount			$	4,385,964.99
11.	Current overcollateralization amount (Pool Balance - Note Balance)			$	4,385,964.99
12.	Weighted Average Coupon			8.78		%
13.	Weighted Average Original Term	months		67.77
14.	Weighted Average Remaining Term	months		24.57
15.	Applicable reference rate for the interest period ending 1/14/2025			N/A
16.	Note Rate applicable to the Class A-2b notes for the interest period ending 1/14/2025			N/A
Collections
17.	Finance Charges:
	a. Collections allocable to Finance Charge			$	2,467,823.84
	b. Liquidation Proceeds allocable to Finance Charge			$	1,193.98
	c. Purchase Amount allocable to Finance Charge			$	0.00
	d. Available Finance Charge Collections (sum a - c)			$	2,469,017.82
18.	Principal:
	a. Collections allocable to Principal			$	17,384,508.99
	b. Liquidation Proceeds allocable to Principal			$	401,934.95
	c. Purchase Amount allocable to Principal			$	0.00
	d. Available Principal Collections (sum a - c)			$	17,786,443.94
19.	Total Finance Charge and Principal Collections (17d + 18d)			$	20,255,461.76
20.	Interest Income from Collection Account			$	63,982.10
21.	Simple Interest Advances			$	0.00
22.	Available Collections (Ln19 + 20 + 21)			$	20,319,443.86


Available Funds
23.	Available Collections	$	20,319,443.86
24.	Reserve Account Draw Amount	$	0.00
25.	Available Funds	$	20,319,443.86
Application of Available Funds
26.	Servicing Fee	0.15		%
	a. Monthly Servicing Fee	$	277,268.83
	b. Amount Unpaid from Prior Months	$	0.00
	c. Amount Paid	$	277,268.83
	d. Shortfall Amount (a + b - c)	$	0.00
27.	Unreimbursed Servicer Advances	$	0.00
28.	Successor Servicer and Asset Representations Reviewer Unpaid Expenses and Indemnity Amounts
	a. Successor Servicer Unpaid Transition Expenses and Indemnity Amounts (Capped at $175,000 annually)	$	0.00
	b. Successor Servicer Amount Paid	$	0.00
	c. Successor Servicer Shortfall Amount (a - b)	$	0.00
	d. Asset Representations Reviewer Fees, Expenses and Indemnity Amounts (Capped at $175,000 annually)	$	0.00
	e. Asset Representations Reviewer Amount Paid	$	0.00
	f. Asset Representations Reviewer Shortfall Amount (d - e)	$	0.00
29.	Class A Noteholder Interest Amounts
	a. Class A-1 Monthly Interest	$	0.00
	b. Additional Note Interest related to Class A-1 Monthly Interest	$	0.00
	c. Interest Due on Additional Note Interest related to Class A-1 Monthly Interest	$	0.00
	d. Total Class A-1 Note Interest (sum a - c)	$	0.00
	e. Class A-2a Monthly Interest	$	—
	f. Additional Note Interest related to Class A-2a Monthly Interest	$	0.00
	g. Interest Due on Additional Note Interest related to Class A-2a Monthly Interest	$	0.00
	h. Total Class A-2a Note Interest (sum e - g)	$	—
	i. Class A-2b Monthly Interest	$	—
	j. Additional Note Interest related to Class A-2b Monthly Interest	$	0.00
	k. Interest Due on Additional Note Interest related to Class A-2b Monthly Interest	$	0.00
	l. Total Class A-2b Note Interest (sum i - k)	$	—
	m. Class A-3 Monthly Interest	$	40,185.12
	n. Additional Note Interest related to Class A-3 Monthly Interest	$	0.00
	o. Interest Due on Additional Note Interest related to Class A-3 Monthly Interest	$	0.00
	p. Total Class A-3 Note Interest (sum m - o)	$	40,185.12
	q. Class A-4 Monthly Interest	$	88,362.17
	r. Additional Note Interest related to Class A-4 Monthly Interest	$	0.00
	r. Additional Note Interest related to Class A-4 Monthly Interest	$	0.00
	t. Total Class A-4 Note Interest (sum q - s)	$	88,362.17
30.	Priority Principal Distributable Amount	$	0.00
31.	Class B Noteholder Interest Amount
	a. Class B Monthly Interest	$	22,658.33
	b. Additional Note Interest related to Class B Monthly Interest	$	0.00
	c. Interest Due on Additional Note Interest related to Class B Monthly Interest	$	0.00
	d. Total Class B Note Interest (sum a - c)	$	22,658.33
32.	Secondary Principal Distributable Amount	$	0.00
33.	Class C Noteholder Interest Amount
	a. Class C Monthly Interest	$	49,343.75
	b. Additional Note Interest related to Class C Monthly Interest	$	0.00
	c. Interest Due on Additional Note Interest related to Class C Monthly Interest	$	0.00
	d. Total Class C Note Interest (sum a - c)	$	49,343.75
34.	Tertiary Principal Distributable Amount	$	0.00
35.	Class D Noteholder Interest Amount
	a. Class D Monthly Interest	$	28,512.50
	b. Additional Note Interest related to Class D Monthly Interest	$	0.00
	c. Interest Due on Additional Note Interest related to Class D Monthly Interest	$	0.00
	d. Total Class D Note Interest (sum a - c)	$	28,512.50


36.	Quaternary Principal Distributable Amount	$	13,628,720.75
37.	Required Payment Amount (Ln 26 + Ln 28 + (sum of Ln 29 through Ln 36))	$	14,135,051.45
38.	Reserve Account Deficiency	$	0.00
39.	Regular Principal Distributable Amount	$	4,385,964.99
40.	Remaining Unpaid Servicer Transition Expenses and Additional Servicing Fees, if any	$	0.00
41.	Remaining Unpaid Trustee and Asset Representations Reviewer Fees, Expenses and Indemnity Amounts, if any
	a. Remaining Unpaid Trustee Fees, Expenses and Indemnity Amounts	$	0.00
	b. Remaining Unpaid Asset Representations Reviewer Fees, Expenses and Indemnity Amounts	$	0.00
42.	Remaining Unpaid Successor Servicer Indemnity Amounts, if any	$	0.00
Collection Account Activity		0.15		%
43.	Deposits
	a. Total Daily Deposits of Finance Charge Collections	$	2,469,017.82
	b. Total Daily Deposits of Principal Collections	$	17,786,443.94
	c. Withdrawal from Reserve Account	$	0.00
	d. Interest Income	$	63,982.10
	e. Total Deposits to Collection Account (sum a - d)	$	20,319,443.86
44.	Withdrawals
	a. Servicing Fee and Unreimbursed Servicer Advances	$	277,268.83
	b. Successor Servicer Transition Expenses and Indemnity Amounts	$	0.00
	c. Deposit to Note Payment Account for Monthly Note Interest/Principal	$	18,243,747.61
	d. Deposit to Reserve Account	$	0.00
	e. Excess Collections (Deposit to Certificate Payment Account for payment to Certificateholder)	$	1,798,427.42
	f. Total Withdrawals from Collection Account (sum a - e)	$	20,319,443.86
Note Payment Account Activity
45.	Deposits
	a. Class A-1 Interest Distribution	$	0.00
	b. Class A-2a Interest Distribution	$	—
	c. Class A-2b Interest Distribution	$	—
	d. Class A-3 Interest Distribution	$	40,185.12
	e. Class A-4 Interest Distribution	$	88,362.17
	f. Class B Interest Distribution	$	22,658.33
	g. Class C Interest Distribution	$	49,343.75
	h. Class D Interest Distribution	$	28,512.50
	i. Class A-1 Principal Distribution	$	0.00
	j. Class A-2a Principal Distribution	$	0.00
	k. Class A-2b Principal Distribution	$	0.00
	l. Class A-3 Principal Distribution	$	18,014,685.74
	m. Class A-4 Principal Distribution	$	0.00
	n. Class B Principal Distribution	$	0.00
	o. Class C Principal Distribution	$	0.00
	p. Class D Principal Distribution	$	0.00
	q. Total Deposits to Note Payment Account (sum a - p)	$	18,243,747.61
46.	Withdrawals
	a. Class A-1 Distribution	$	0.00
	b. Class A-2a Distribution	$	0.00
	c. Class A-2b Distribution	$	0.00
	d. Class A-3 Distribution	$	18,054,870.86
	e. Class A-4 Distribution	$	88,362.17
	f. Class B Distribution	$	22,658.33
	g. Class C Distribution	$	49,343.75
	h. Class D Distribution	$	28,512.50
	i. Total Withdrawals from Note Payment Account (sum a - h)	$	18,243,747.61


Certificate Payment Account Activity
47.	Deposits to Certificate Payment Account from Excess Collections	$	1,798,427.42
48.	Withdrawals from Certificate Payment Account for Certificateholder Distribution	$	1,798,427.42
Required Reserve Account Amount		0.15		%
49.	Required Reserve Account Amount (1.00% of Initial Pool Balance)	$	4,385,964.99
Reserve Account Reconciliation
50.	Beginning Balance (as of end of preceding Distribution Date)	$	4,385,964.99
51.	Investment Earnings	$	16,697.62
52.	Reserve Account Draw Amount	$	0.00
53.	Reserve Account Amount (Ln 50 + Ln 51 - Ln 52)	$	4,402,662.61
54.	Deposit from Available Funds (Ln 44d)	$	0.00
55.	If Reserve Account Balance exceeds Required Reserve Account Amount, payment to
	a. the Note Payment Account for the payment of principal to the extent of any unfunded Regular Principal Distribution Amount; and	$	0.00
	b. any Successor Servicer for the payment of any unfunded Transition Costs and Additional Servicing Fee	$	0.00
56.	Payment to Depositor if Reserve Account Balance exceeds Required Reserve Account Amount and to the extent no unfunded amounts described in Ln 55 exist	$	16,697.62
57.	Ending Balance (Ln53 + Ln54 - Ln55 - Ln56)	$	4,385,964.99
58.	Reserve Account Deficiency (Ln50 - Ln57)	$	0.00
Instructions to the Trustee
59.	Amount to be deposited from the Reserve Account into the Collection Account	$	0.00
60.	Amount to be paid to Servicer from the Collection Account	$	277,268.83
61.	Amount to be deposited from the Collection Account into the Note Payment Account	$	18,243,747.61
62.	Amount to be deposited from the Collection Account into the Certificate Payment Account	$	1,798,427.42
63.	Amount to be deposited from the Collection Account into the Reserve Account	$	0.00
64.	Amount to be deposited from the Reserve Account, if Reserve Account Balance exceeds Required Reserve Account Amount, into
	a. the Note Payment Account for any unfunded Regular Principal Distributable Amount	$	0.00
	b. the Depositor, if no unfunded Regular Principal distributable amount exists	$	16,697.62
65.	Amount to be paid to Class A-1 Noteholders from the Note Payment Account	$	0.00
66.	Amount to be paid to Class A-2a Noteholders from the Note Payment Account	$	0.00
67.	Amount to be paid to Class A-2b Noteholders from the Note Payment Account	$	0.00
68.	Amount to be paid to Class A-3 Noteholders from the Note Payment Account	$	18,054,870.86
69.	Amount to be paid to Class A-4 Noteholders from the Note Payment Account	$	88,362.17
70.	Amount to be paid to Class B Noteholders from the Note Payment Account	$	22,658.33
71.	Amount to be paid to Class C Noteholders from the Note Payment Account	$	49,343.75
72.	Amount to be paid to Class D Noteholders from the Note Payment Account	$	28,512.50
73.	Amount to be paid to Certificateholders from the Certificate Payment Account with respect to Excess Collections	$	1,798,427.42


Delinquency Activity
		Number of Loans	Principal Balance
74.	Delinquency Analysis
	a. 31 to 60 days past due	1,740	$	19,169,459.06
	b. 61 to 90 days past due	813	$	9,521,302.36
	c. 91 to 120 days past due	176	$	1,813,703.70
	d. 121 or more days past due	0	$	0.00
	e. Total Past Due (sum a - d)	2,729	$	30,504,465.12
	f. Delinquent Loans as a percentage of end of period Pool Balance (Ln 74e / Ln 5)		9.6929		%

75.	Has a Delinquency Trigger Event occurred?		No

Loss Activity
		Number of Loans	Principal Balance

76.	Defaulted Receivables (charge-offs)	82	$	630,176.75
77.	Recoveries	240	$	403,128.93
78.	Net Losses (Ln 76 - Ln 77)		$	227,047.82
79.	Ratio of Net Losses to Beginning of Period Pool Balance (Ln 78 / Ln 1)		0.0682		%

Cumulative Loss Activity
		Number of Loans	Principal Balance

80.	Defaulted Receivables (charge-offs)	4,502	$	65,854,348.60
81.	Recoveries	3,761	$	30,803,894.95
82.	Cumulative Net Losses (Ln 80 - Ln 81)		$	35,050,453.65
83.	Ratio of Cumulative Net Losses to Initial Pool Balance (Ln 82 / Ln 7)		1.9979		%
84.	Average Net Loss on Defaulted Receivables		$	7,785.53

Other Servicing Information

85.	Principal Balance of Receivables extended during the Collection Period		$	5,681,841.95
86.	Pool Balance on the close of the last day of the preceding Collection Period		$	332,722,596.89
87.	Ratio of extensions to pool balance (Ln 85 / Ln 86)		1.71		%

IN WITNESS WHEREOF, the undersigned has duly executed this certificate on January 9, 2025.


CARMAX BUSINESS SERVICES, LLC

As Servicer

By:			/s/ Greg Dostich

Name:			Greg Dostich

Title:			Vice President and Treasurer

CarMax Auto Owner Trust 2021-3 10-D