Filing a lien release in Illinois is very straightforward. All that's required is a lien release form to be filed in the Recorder of Deeds office where the intial lien claim was filed.
You should file this release as soon as possible. Under §770 ILCS 60/35 if the owner sends a written demand for the release of a satisfied lien claim, the claimant must release the lien within 10 days of receipt of the demand. Failure to do so can expose the claimant to liability for $2,500 and any reasonable attorney fees the owner incurs to collect that penalty.