Yes, OBLIGATION is a Scrabble word!

Letter values in Scrabble US: O 1, B 3, L 1, I 1, G 2, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

the social force that binds you to the courses of action demanded by that force; every opportunity, an obligation; every possession, a duty"- John D.Rockefeller Jr
the state of being obligated to do or pay something
a personal relation in which one is indebted for a service or favor
a written promise to repay a debt
a legal agreement specifying a payment or action and the penalty for failure to comply

Also: debt instrument, certificate of indebtedness.