Allowed patents require maintenance in the form of a fee. Maintenance fees must be paid on all allowed utility patents. Nothing is really gained by paying the maintenance fee, no fancy certificate is sent out, no special tune-up is performed, but if the owner doesn't pay, the PTO abandons the patent, causing it to expire before the set term has run its course. So the inventor must pay the maintenance fee in order to keep the benefits gained by the patent.

Maintenance fees are due at three time periods throughout the life of the patent; 3.5, 7.5, and 11.5 years after the granting of the patent. There is also a 6 month grace period, but paying during the grace period requires paying a surcharge in addition to the payment of the maintenance fee. If the payment is not sent in before the expiration of the grace period, the patent will expire.

It may be possible to revive a patent that was abandoned due to a missing maintenance fee, but that requires a hefty petition fee in addition to paying the late maintenance fees.