If your boss -- who fired you -- accidentally gave you an extra $40,000 ... would you give it back?
Didn't think so.
And that's the problem the Washington Redskins are facing ... 'cause they just filed a lawsuit claiming they accidentally issued a $40,000 check to a player they cut back in 2012 ... and he won't give it back.
The man with the extra dough is H.B. Blades -- who was on the Redskins' main roster from 2007 to 2010.
The team says it officially cut ties with Blades in 2012 and gave him a $40,000 severance check for his troubles.
The problem ... they "mistakenly paid an additional $40,000 to Blades on Dec. 27, 2013 as a result of a clerical error."
But sadly, the team says it realized the mistake and demanded the money back -- but Blades refuses to pony it up. So, the Skins took their gripe to the judge ... filing suit in NY federal court.
We reached out to Blades for comment -- so far, no word back.