As announced on the USPTO website, as of June 30, 2012, there will be a daily limit of $49,999.99 for credit card accounts, but no daily limit for debit card accounts. (Currently, the daily limit for both credit card and debit card accounts is $99,999.99.) The new limit will be enforced automatically through the Pay.gov system, and any transaction that would exceed the limit will be rejected. Notably, the new cap may be too low for even a single Request for Inter Partes Review or Post Grant Review depending on the number of patent claims at issue.
(The USPTO also accepts payment by deposit account, electronic funds transfer (EFT) over the USPTO Website, and wire transfer through the Federal Reserve Fedwire System.)