The 2020 CO Plan provides for the issuance of CO Incentive Units to CarOffer’s employees, officers, managers, and consultants. The 2020 CO Plan authorized up to an aggregate of 485,714 CO Incentive Units for such issuances.

The Vesting Agreement provides for the vesting of the Subject Units beneficially owned by the T5 Holders, which vest in accordance with the terms described in Note 2 of the Unaudited Condensed Consolidated Financial Statements included elsewhere in this Quarterly Report.

The 2021 CO Plan provides for an incentive equity grant structure whereby 2021 Incentive Units will be granted to CIE and 2021 CO Plan grantees will receive an associated CIE Interest, with back-to-back vesting between the 2021 Incentive Units and the associated CIE Interest. The 2021 CO Plan authorized up to an aggregate of 228,571 2021 Incentive Units for such issuances.

The following two tables show stock compensation expense by award type and where the stock compensation expense is recorded in the Company’s Unaudited Condensed Consolidated Income Statements:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Options	$	630	$	—	$	1,882	$	17
Restricted stock units		13,852		11,030		41,539		34,617
CO Incentive Units and Subject Units		687		—		9,681		—
Total stock-based compensation expense	$	15,169	$	11,030	$	53,102	$	34,634


	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Cost of revenue	$	110	$	57	$	311	$	241
Sales and marketing expense		2,717		2,450		9,040		8,206
Product, technology, and development expense		5,583		5,140		17,585		15,861
General and administrative expense		6,759		3,383		26,166		10,326
Total stock-based compensation expense	$	15,169	$	11,030	$	53,102	$	34,634

Excluded from stock-based compensation expense is $777, $656, $2,212 and $1,323 of capitalized website development and internal-use software costs for the three months ended September 30, 2021 and 2020 and the nine months ended September 30, 2021 and 2020, respectively.

During the three months ended September 30, 2021 and 2020 and the nine months ended September 30, 2021 and 2020, the Company withheld 114,973, 111,370, 404,626 and 337,313 shares of Class A common stock, respectively, to satisfy employee tax withholding requirements and for option exercise costs due to net share settlements and cashless exercises of options. The shares withheld return to the authorized, but unissued pool under the 2017 Plan and can be reissued by the Company. Total payments to satisfy employee tax withholding requirements and for option exercise costs due to net share settlements and cashless exercises of options were $3,106, $2,922, $11,314 and $8,708 for the three months ended September 30, 2021 and 2020 and the nine months ended September 30, 2021 and 2020, respectively, and are reflected as a financing activity within the Unaudited Condensed Consolidated Statements of Cash Flows.