CUSIP No. 01626W101 13D Page 39 of 43

EXHIBIT 99.A

JOINT FILING AGREEMENT

Pursuant to and in accordance with the Securities Exchange Act of 1934, as amended, and the rules and regulations thereunder (the “Exchange Act”) the undersigned hereby agree to the joint filing on behalf of each of them of any filing required by such party under Section 13 of the Exchange Act or any rule or regulation thereunder (including any amendment, restatement, supplement, and/or exhibit thereto) with respect to securities of Alight, Inc., a Delaware corporation, and further agree to the filing, furnishing, and/or incorporation by reference of this agreement as an exhibit thereto. Each of them is responsible for the timely filing of such filings and any amendments thereto, and for the completeness and accuracy of the information concerning such person contained therein; but none of them is responsible for the completeness or accuracy of the information concerning the other persons making the filing, unless such person knows or has reason to believe that such information is inaccurate. This agreement shall remain in full force and effect until revoked by any party hereto in a signed writing provided to each other party hereto, and then only with respect to such revoking party. This agreement may be executed in any number of counterparts all of which taken together shall constitute one and the same instrument.

Date: July 12, 2021

BLACKSTONE CAPITAL PARTNERS VII NQ L.P.
By: Blackstone Management Associates VII NQ L.L.C., its general partner
By: BMA VII NQ L.L.C., its sole member By: Blackstone Holdings II L.P., its managing member
By: Blackstone Holdings I/II GP L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director

CUSIP No. 01626W101 13D Page 40 of 43

BCP VII SBS HOLDINGS L.L.C.
By: Blackstone Side-by-Side Umbrella Partnership L.P., its sole member
By: Blackstone Side-by-Side Umbrella GP L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Manager
BLACKSTONE FAMILY INVESTMENT PARTNERSHIP VII-ESC NQ L.P.
By: BCP VII Side-by-Side GP NQ L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Authorized Signatory
BTAS NQ HOLDINGS L.L.C.
By: BTAS Associates-NQ L.L.C., its managing member
By: Blackstone Holdings II L.P., its managing member
By: Blackstone Holdings I/II GP L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
BLACKSTONE CAPITAL PARTNERS VII (IPO) NQ L.P.
By: Blackstone Management Associates VII NQ L.L.C., its general partner
By: BMA VII NQ L.L.C., its sole member
By: Blackstone Holdings II L.P., its managing member
By: Blackstone Holdings I/II GP L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director

CUSIP No. 01626W101 13D Page 41 of 43

BLACKSTONE MANAGEMENT ASSOCIATES VII NQ L.L.C.
By: BMA VII NQ L.L.C., its sole member
By: Blackstone Holdings II L.P., its managing member
By: Blackstone Holdings I/II GP L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
BMA VII NQ L.L.C.
By: Blackstone Holdings II L.P., its managing member
By: Blackstone Holdings I/II GP L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
BLACKSTONE HOLDINGS II L.P.
By: Blackstone Holdings I/II GP L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
BLACKSTONE SIDE-BY-SIDE UMBRELLA PARTNERSHIP L.P.
By: Blackstone Side-by-Side Umbrella GP L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Manager
BLACKSTONE SIDE-BY-SIDE UMBRELLA GP L.L.C.
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Manager

CUSIP No. 01626W101 13D Page 42 of 43

BLACKSTONE HOLDINGS III L.P.
By: Blackstone Holdings III GP L.P., its general partner,
By: Blackstone Holdings III GP Management L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
BLACKSTONE HOLDINGS III GP L.P. By: Blackstone Holdings III GP Management L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
BLACKSTONE HOLDINGS III GP MANAGEMENT L.L.C.
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
BCP VII SIDE-BY-SIDE GP NQ L.L.C.
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
BTAS ASSOCIATES-NQ L.L.C.
By: Blackstone Holdings II L.P., its managing member
By: Blackstone Holdings I/II GP L.L.C., its general partner
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
BLACKSTONE HOLDINGS I/II GP L.L.C.
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director

CUSIP No. 01626W101 13D Page 43 of 43

THE BLACKSTONE GROUP INC.
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
BLACKSTONE GROUP MANAGEMENT L.L.C.
By:	/s/ Tabea Hsi
Name:	Tabea Hsi
Title:	Senior Managing Director
By:	/s/ Stephen A. Schwarzman
Name:	Stephen A. Schwarzman