Maintenance fees are required to keep in force all utility and reissue utility patents based on applications filed on or after December 12, 1980. Maintenance fees are not required for a design or plant patent, or for statutory invention registrations. Maintenance fees can be paid without a surcharge at 3 to 3.5 years, 7 to 7.5 years, and 11 to 11.5 years, after the date of issue. A maintenance fee cannot be paid early. Maintenance fees may also be paid with a surcharge during the “grace periods” at 3.5 to 4 years, 7.5 to 8 years, and 11.5 to 12 years after the date of issue.