After all of the estate's property has been distributed and all fees paid, the probate court will formally discharge the executor. Typically, this is a standard form that must be presented to the court for the judge's signature. The order of discharge is an important legal document. The executor should keep it in a safe place with other important papers. The executor is entitled to a fee for his services.
Fees are a matter of state law and vary state by state.
In some states, the fee is based on a percentage of the estate's value. This might happen if there are newly discovered assets, or a will is found after it was thought that there was no will. If assets of the deceased are discovered after the estate is closed, the executor needs to petition the probate court to reopen the estate to administer the assets. In most states this procedure will not be a full-blown probate. As a rule, creditors will have no claim on the newly discovered assets - the assets merely need to be distributed according to the terms of the will.