This brief note is not legal advice and is for educational purposes only.
When a utility patent (non-provisional) issues (always on a Tuesday) it has an issue (grant) date. This issue date is important for a variety of reasons, one being that to keep a patent “in force” for infringement or litigation purposes you must pay a patent maintenance fee
Unlike most foreign countries which have an annual maintenance fee (annuity), in the United States the maintenance fee is due 3 different times. If not paid the patent will eventually expire (after the grace period – explained below (35 USC. §41(b)).
The maintenance fee must be paid within a payment “window” that extends for a 1 year period from when it opens.
The windows open at 3, 7, and 11 years after the patent issue date and close 1 year later (thus they are called the 4th, 8th, and 12th year).
When the window opens and for 6 months thereafter only the maintenance fee is due (37 CFR 1.362(d)). If you pay in the later 6 months (the grace period), then the maintenance fee is due as well as a maintenance surcharge (37 CFR 1.362(e)).
Be aware that maintenance fees are subject to change and if your entity status has changed then the maintenance fee changes.
The easiest way to check what is due and the dates is to have this information available:
Go to this link, check, and pay it.
Pay the maintenance fee before the 3.5, 7.5, and 11.5 years after issue to avoid the maintenance fee surcharge and you might want to pay as soon as a window opens to avoid possible fee increases.
If you would rather have us pay the fee, then we charge an hour of our time plus the fees.
Clearly you would not pay a maintenance fee if the patent term had expired. For example, if it took 10 years to get the parent patent issued, and without a patent term extension, you would not pay the 12th year fee. Similarly a check should be made to see if a terminal disclaimer was filed.
Also note that a design or plant patent has no maintenance fees.