Utility and plant patents are valid for 20 years from the date of application, provided that maintenance fees are paid at 3.5, 7.5 and 11.5 years after the date of issue. If a maintenance fee is not paid, the patent expires and the invention becomes public domain. According to the 2010 Four Offices Statistics Report, approximately 50 percent of U.S. patents are maintained for at least 16 years.
Design patents are valid for 14 years from the date of issue. Maintenance fees are not required.
Table 1. Utility and Plant* Patent Terms, 1790-present
| Years | Term |
|---|---|
| 1995-present | 20 years from date of filing |
| 1861-1995 | 17 years from date of grant |
| 1836-1861 | 14 + 7 year extension (optional) |
| 1790-1836 | 14 years |
*Plant patents were first issued in 1931.
Table 2. Design Patent Terms, 1842-present
| Year | Term |
|---|---|
| 2015-present | 15 years from date of grant |
| 1981-2015 | 14 years from date of grant |
| 1861-1981 | 3.5, 7 or 14 years |
| 1842-1861 | 7 years |
Patent Librarian's Notebook 