Yes, COMMERCES is a Scrabble word!

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

Is it a valid word?

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

transactions (sales and purchases) having the objective of supplying commodities (goods and services)
the United States federal department that promotes and administers domestic and foreign trade (including management of the census and the patent office); created in 1913
social exchange, especially of opinions, attitudes, etc.

Also: department of commerce, commerce department.