What are the due years for maintenance fees for utility patents?

Maintenance fees for utility patents are critical to keep a patent in force, and they are due at specific intervals after the patent is granted. The correct timeline for the payment of these fees is set at 3.5 years, 7.5 years, and 11.5 years from the date of the patent grant.

The first maintenance fee is due at 3.5 years, which allows the patent holder to maintain their rights for the first period. The subsequent payments are then structured at 7.5 years and 11.5 years, ensuring that the patent remains enforceable as long as the fees are duly paid.

Understanding this payment schedule is essential for patent holders to avoid abandonment of their patents due to failure to pay the required maintenance fees on time.