After your utility patent is granted, you must pay fees in order for the patent to remain in force. These “maintenance fees” must be paid 3.5 years, 7.5 years, and 11.5 years after the patent is granted. The patent office offers a six month grace period so fees may be paid, with a surcharge, by the 4th, 8th, or 12th year after grant. Failure to pay the fees will result in the patent expiring. After expiration, however, you may petition the Director of the United States Patent and Trademark Office to accept a late maintenance fee and reinstate your patent. This may be done at any time if the delay was unavoidable. If the delay was unintentional, the petition must be filed within two years of the expiration of the grace period. In either case, the petition must include the required maintenance fee, a surcharge, and an appropriate statement that the delay was unavoidable or unintentional. If the petition is refused, you may file another petition for reconsideration within two month of the refusal. There are no maintenance fees due for plant or design patents.