Several Contractors use on-line Billing ex. Textura Procore etc. You can not bill retainage to the GC until the Project is Complete and they open Retainage for you to Bill. What are our rights to file a lien concerning Retainage? Can we bill & file on retainage we bill outside of the on-line systems even though the GC rejects The Billing saying that the job is not Complete and Retainage is not billable?