No, you can't do this--you cannot bind them to accept $5k as payment in full without their agreement. Unfortunately for you, they may cash or deposit the check without agreeing to your terms, since if someone is owed money, the law allows them to cash/deposit any payments they receive and apply it to that amount. Since they have the legal right to cash/deposit the check, they do not give up any rights by doing so--and will not be deemed to have agreed to accept it as final payment or payment in full.Everyone would do what you suggest if the law allowed it--send in a partial payment marked "final payment" or "payment in full"--and debts would be worthless; that's why the law does not allow this.