We are a supplier working on a public project, with some invoiced items that are past due by several months. The are different purchase orders for the multiple material supplied. We need to know what the legalities are for withholding delivery of pending material (it's ready to ship) until payment on delinquent account is settled. And, we need to know what the legalities are for us changing payment terms on the pending material to Cash In Advance.
As Nate stated, whether or not you are entitled to withhold further deliveries based on non-payment depends on the terms of your contract. But a better focus to ensure payment, with considerably lower risk of backlash, would be to pursue the overdue amounts via a stop payment notice (if your contract is with the GC or if you served preliminary notice) or via a payment bond claim. All public works projects in California over $25,000.00 are required to have a payment bond. If the amounts for the overdue materials are undisputed it should be relatively straight forward get payment directly from the surety And the mere threat to do so should also encourage direct payment without delay.
If you require legal assistance feel free to email me at ryan@huntortmann.com to schedule a free consultation.
Unless our bound to certain terms under an agreement already, you can sell future materials on any terms that you see fit - including Cash In Advance. And, unless there are agreed upon terms otherwise, you don't have to sell further materials to the buyer until you are paid for the materials already provided.