Legal Question in Constitutional Law in Florida

I am assuming you have nothing in writing except the check.They can try to put a lien on your house. I doubt it is worth it for them to pursue that for $100.00. As far as whether them cashing the check is proof that they accepted payment, well sure it is. But, the issue is whether it is proof of payment in full. If you wrote on the check "paid in full" or something similar, then if they cash it they have accepted it as payment in full and you're done. However, there is no law preventing them from accepting partial payments until the job is completed and they may argue that is what occurred if you have to fight about it.