A "Prox 60" payment term means that the clock on invoice aging starts at the end of a given month rather than upon actual receipt of the invoice. Example: ACME Widget's AR department invoices customer SlyFox, Inc. weekly for goods and services performed the week before. ACME invoices SFI on Jan 7, 14, 21 and Jan 28. With a Net 60, the invoices would each be due no later than 60 days from the issue date. So, (basically) March 7, 14, 21 and March 28. With a Prox 60, all four invoices are due no later than March 31, because the 60 day payment "clock" for any January invoice doesn't kick in until January 31. Prox 60 is a pretty sweet deal for a buyer. Simplified AP and what amounts to a Net 85 term for early month billing. Because of this, Prox 60 is hard to come by and the savvy business provider will either avoid it altogether or will adjust pricing and other contract terms accordingly. Hope this helps.