I am a steel subcontractor working on a public job in Alabama. I have two separate "contracts" for this job. A purchase order for the steel materials and a subcontract for the steel field erection services. The GC has had all kinds of problems on this job and is likely facing some liquidated damages. As such they are looking for every possible pocket to back charge including mine. No matter how false the claims, they are using a "throw it against the wall" approach and see what sticks. Yesterday the informed me they are holding payment until they can confirm or argue many of their so called "back charges" for delays. So, I would like to file liens to protect myself. (a) do I need to file separate liens for the PO and the subcontract? I would think I would? (b) I currently have billing that is 20 days past due and more coming due in about 15 days. Can I only file for the past due amounts or should I file for all amounts due? Thanks,