Yes, CHECKSUMS is a Scrabble word!

Letter values in Scrabble US: C 3, H 4, E 1, C 3, K 5, S 1, U 1, M 3, S 1.

Is it a valid word?

CHECKSUMS is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

a digit representing the sum of the digits in an instance of digital data; used to check whether errors have occurred in transmission or storage