Yes, RESCISSION is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, S 1, C 3, I 1, S 1, S 1, I 1, O 1, N 1.

Is it a valid word?

RESCISSION is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

(law) the act of rescinding; the cancellation of a contract and the return of the parties to the positions they would have had if the contract had not been made

Not playable in Scrabble US: RECISSION.