Stock-based compensation expense was $118 million in 2023, $111 million in 2022 and $85 million in 2021. The Company recognized income tax benefits related to stock-based compensation of $24 million in 2023, $26 million in 2022 and $16 million in 2021.

The Company’s equity incentive compensation plan allows for the issuance of various forms of stock-based compensation, including stock options, restricted stock and restricted stock units, including performance-based awards. At December 31, 2023 and 2022, respectively, there were 4,218,093 and 1,650,696 shares available for future grant under the Company’s equity incentive compensation plan.

Stock awards granted to employees are comprised of restricted stock and restricted stock units. Stock awards generally vest over three years. The Company may issue shares from treasury stock to the extent available or issue new shares. There were no restricted shares issued in 2023, 2022 or 2021. The number of restricted stock units issued was 752,534 in 2023, 548,926 in 2022 and 636,956 in 2021, with a weighted-average grant date fair value of $116 million, $93 million and $84 million, respectively. Unrecognized compensation expense associated with restricted stock and restricted stock units, inclusive of those awards assumed in the acquisition of People's United, was $42 million as of December 31, 2023 and is expected to be recognized over a weighted-average period of approximately one year.

A summary of restricted stock and restricted stock unit activity follows:


	Restricted Stock Units Outstanding			Weighted- Average Grant Price		Restricted Stock Outstanding			Weighted- Average Grant Price
Unvested at January 1, 2023		1,167,582		$	156.23		75,006		$	164.65
Granted		752,534			153.86		—			—
Vested		(543,987	)		156.97		(35,777	)		164.66
Cancelled		(45,851	)		159.73		(7,514	)		164.66
Unvested at December 31, 2023		1,330,278		$	154.46		31,715		$	164.63

Stock options granted to employees generally vest over three years and are exercisable over terms not exceeding ten years and one day. The Company granted 179,551, 138,825 and 178,441 stock options in 2023, 2022 and 2021, respectively. The weighted-average grant date fair value of options granted was $9 million in 2023, $6 million in 2022 and $5 million in 2021. The Company used an option pricing model to estimate the grant date present value of stock options granted.

A summary of stock option activity follows:


				Weighted-Average
	Stock Options Outstanding			Exercise Price		Life (In Years)		Aggregate Intrinsic Value (In millions)
Outstanding at January 1, 2023		2,340,062		$	148.78
Granted		179,551			156.00
Exercised		(262,837	)		122.45
Expired		(58,112	)		155.87
Outstanding at December 31, 2023		2,198,664		$	152.33		5.6	$	6
Exercisable at December 31, 2023		1,807,515		$	151.67		5.0	$	5

For 2023, 2022 and 2021 M&T received $32 million, $37 million and $305 thousand, respectively, in cash from the exercise of stock options. The intrinsic value of stock options exercised and the related tax benefit realized by the Company were not material in any of those three years. As of December 31, 2023, the amount of unrecognized compensation cost related to non-vested stock options was not material. The total grant date fair value of stock options vested during 2023, 2022 and 2021 was not material. Upon the exercise of stock options, the Company may issue shares from treasury stock to the extent available or issue new shares.

The stock purchase plan provides eligible employees of the Company with the right to purchase shares of M&T common stock at a discount through accumulated payroll deductions. In connection with the employee stock purchase plan, shares of M&T common stock issued were 90,575 in 2023, 75,232 in 2022 and 95,147 in 2021. As of December 31, 2023, there were 1,972,627 shares available for issuance under the plan. M&T received cash for shares purchased through the employee stock purchase plan of $13 million in 2023 and $11 million in each of 2022 and 2021. Compensation expense recognized for the stock purchase plan was not material in 2023, 2022 or 2021.

The Company provided a deferred bonus plan pursuant to which eligible employees could elect to defer all or a portion of their annual incentive compensation awards and allocate such awards to several investment options, including M&T common stock. The deferred bonus plan was frozen effective January 1, 2010 and did not allow any additional deferrals after that date. Participants could elect the timing of distributions from the plan. Such distributions are payable in cash with the exception of balances allocated to M&T common stock which are distributable in the form of M&T common stock. Shares of M&T common stock distributable pursuant to the terms of the deferred bonus plan were 10,238 and 11,725 at December 31, 2023 and 2022, respectively. The obligation to issue shares is included in “common stock issuable” in the Consolidated Balance Sheet.

The Company maintains compensation programs for members of the Company’s boards of directors and its regional director advisory councils that provides for a portion of their compensation to be received in shares or restricted stock units. In 2023 and 2022, 27,027 and 22,068 shares, respectively, were granted under such programs.

Through acquisitions, the Company assumed obligations to issue shares of M&T common stock related to deferred directors' compensation plans. Shares of common stock issuable under such plans were 1,979 and 2,306 at December 31, 2023 and 2022, respectively. The obligation to issue shares is included in “common stock issuable” in the Consolidated Balance Sheet.