We are mid construction on a larger custom SFR. Our HVAC sub is scheduled for a 60k payment for delivery of materials. Materials are onsite. We typically want a waiver from his material supplier or to pay the supplier directly to eliminate any chance of the supplier filing a lien against the project. Our sub is telling us they have accounts with different suppliers, none of whom receive any information about projects and so cannot file a lien. How can I verify this?