It is common practice for terms of service to indicate that to the extent the supplier is supporting a federal contract, certain FAR (etc) clauses shall be incorporated into the purchase order; and if it is in support of a grant, certain other requirements are incorporated. What is not typically addressed in the terms of service, however, is how a supplier will know if a PO is in support of a federal contract/grant. It is not practical for many contractors to include this information on the PO - especially when a supplier is supporting numerous customers, some of which may be federal. When it is not practical to id each and every PO that may be considered a subk, what are best practices for putting supplier on notice - or is notice even required?