If your contract allows for the withholding of contractual retainage, then before you can file a Lien for unpaid contractual retainage, you must serve a Notice of Contractual Retainage on the Property Owner and General Contractor by the earlier of: (1) 30 days of completing the work under your contract; or (2) within 30 days of completion of the overall Project. The Lien Professor’s “All Inclusive Mechanics Lien Kit” contains a Notice of Contractual Retainage, along with detailed instructions on how to prepare and serve the Notice.