We are a subcontractor and the GC we are working for is asking us to sign and notarize progress payment line waivers for amounts they have not paid us for, is this legal? They are 60 days behind on our payment yet they are refusing to give us payment until we sign the waivers for amounts we have not received yet. We were advised this is fraudulent and we are supposed to sign and notarize at the time we receive our payment.