I didn't notice if there was a specification about transaction date vs. post date, but if it's really important (big tax transaction, for example), I'd be doing it a few days earlier to make sure it posts in time. Even if you can convince them to retroactively credit you the points, it's going to be a hassle I'd rather avoid at the cost of posting the transaction a few days earlier than planned (especially since with a grace period you're likely not even coming out of pocket until the next due date anyways).