What is the (Federal) Government Purchase Card, really?
Upfront: The “GPC” is a payment method, not “credit.”
Although it is functionally a “credit card” that works the same as any other at the cash register, the GPC is far from a credit card in reality.
Before a cardholder can actually legally use the GPC to pay the merchant/vendor, a “Request For Purchase” (RFP) has to be fully processed, including approval from the Billing Official. It is the Billing Official who will review all transactions on the monthly statement to “certify” that every purchase was legal & proper (etc.). The approval for the purchase/payment is required in advance of using it.
So What? Government cardholders who buy from you using the GPC already have an exact and pre-approved use that is permitted. Don’t try to sell add-ons, or upsizing, or extras. It only makes the situation awkward and potentially a big problem if the cardholder goes beyond the pre-approval. Misuse of the card is on the cardholder – it is the (primarily) cardholder that is personally liable for unapproved use of the GPC.
Bottom Line: If you are dealing with a GPC purchase or payment, stick to exactly what the cardholder is pre-approved to do. It saves everyone lots of headaches. It is a method of payment, not a “credit” line for the government employee, and there is very little discretion for when and how it is used.