>Most card
>companies won't let you pay until the transaction is posted.

but I want to note that American Express allows me to pay for transactions once they are pending on the card. I don't have to wait until the business day or so when the transaction will actually post to the account. The Amex mobile app allows for making payments the same day of the transaction. I imagine the same could be possible if using a regular browser to track transactions, but I'm not 100% sure.

I notice with Discover and Capital One (VISA), that isn't the case. Having to wait the business day or two for transactions to post to those accounts can be tricky.