Update: Got this resolved.

I called Southside Auto Sale and explained that I had missed the 24-hour validity period on the original invoice. They confirmed the situation and issued a new invoice with an updated validity period.

I also had them confirm the vehicles, purchasing entity, total amount due and transportation details before making the payment.

So the solution was pretty simple: don’t send payment against an expired invoice. Contact the auction company, have the invoice reissued, and verify all the details on the new invoice before paying.

Thanks to everyone who replied. The advice to call first and get everything confirmed saved me from having to deal with a payment tied to outdated paperwork.

For other dealers buying larger fleets, I’d definitely recommend checking the invoice validity period as soon as you receive it.