Yes, AFFIDAVITS is a Scrabble word!

Letter values in Scrabble US: A 1, F 4, F 4, I 1, D 2, A 1, V 4, I 1, T 1, S 1.

Is it a valid word?

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

written declaration made under oath; a written statement sworn to be true before someone legally authorized to administer an oath