Legal Question in Criminal Law in Illinois

Accusations are easily made, of course, but these people seem like they're playing some kind of game. You don't mention whether you have any kind of written construction contract. You need to look through it for your remedies in case of owner default (like non-payment). Assuming you have something in the nature of a "typical" contract, and if you substantially completed and simply owe them a punch list you might want to suggest a walk-thru and that claiming "forgery" really won't help them get any happier with the work; maybe they're unsophisticated and don't understand that the punch-list is really their "remedy". If they persist, sometimes the best defense is a good offense -- if they owe you money you can say you'll have to lien the house. Without seeing the contract, if any, it is impossible to say how it can help, but hopefully they're not setting you up for some kind of license suspension/revocation.