What happens if a maintenance fee is paid in the wrong amount?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

If a maintenance fee is paid in the wrong amount, the following applies:

• If the fee paid is insufficient, the patent will expire unless the remaining balance is paid within the grace period along with any surcharge.
• If the fee paid exceeds the required amount, a refund may be requested.

As stated in MPEP 2575: “If the amount of the maintenance fee is paid in error … the patentee may file a request for refund … Likewise, if the payment of the maintenance fee was insufficient, the Office will notify the patentee of the deficiency and grant a grace period to permit the deficient amount to be paid …”