You cannot actually buy a patent that has run its full 20-year term, because that invention now belongs to the public and no paperwork brings it back. What people usually mean when they ask how to buy an expired patent is how to acquire one that lapsed early because the owner stopped paying maintenance fees. Those patents still have years of term left on paper, and federal law lets a new owner take assignment from the current holder and petition the USPTO to reinstate the patent under 37 CFR 1.378.1eCFR. 37 CFR 1.378 – Acceptance of Delayed Payment of Maintenance Fee in Expired Patent To Reinstate Patent The rest of this walks through how to tell the two situations apart and, if you’re in the second one, how to complete the purchase and reinstatement.
Expired for Term vs. Lapsed for Nonpayment
A utility patent lasts 20 years from its filing date.2Office of the Law Revision Counsel. 35 USC 154 – Contents and Term of Patent; Provisional Rights After 20 years, it’s gone. Anyone can make, use, or sell the invention, and no petition or payment revives it.
A lapsed patent is different. Utility patents require maintenance fees at 3.5, 7.5, and 11.5 years after grant.3Office of the Law Revision Counsel. 35 USC 41 – Patent Fees; Patent and Trademark Search Systems Miss one, let the six-month grace period pass, and the patent expires for nonpayment even though the 20-year clock hasn’t run out. That gap between early lapse and the true end of term is what makes the reinstatement route possible.
One boundary worth flagging: design and plant patents don’t carry maintenance fees. They run their full term without any payment obligation, so if one has expired, it has expired for good. The buy-and-reinstate strategy only works for utility patents (and reissue utility patents) that lapsed because a fee went unpaid.
Confirm the Patent Still Has Term Left
Before anything else, work out how much life the patent has left. Subtracting 20 years from the filing date is a rough starting point, but two adjustments can move the real expiration date in either direction.
Patent Term Adjustment (PTA) extends the life of a patent when the USPTO caused delays during examination. Under 35 U.S.C. § 154(b), the office calculates PTA at issuance and prints it on the face of the patent.4United States Patent and Trademark Office. Explanation of Patent Term Adjustment Calculation A patent with 400 days of PTA effectively expires 400 days later than the filing date alone would suggest.
Terminal disclaimers cut the opposite way. When the original owner filed a disclaimer during prosecution, often to overcome a double-patenting rejection, the patent expires on the disclaimer date rather than the standard 20-year mark.5United States Patent and Trademark Office. MPEP 2701 – Patent Term A disclaimer can tie the patent’s end date to an earlier patent’s expiration, which sometimes wipes out most of the apparent remaining term. Check the file history for one before you talk price.
Check the Maintenance Status
The USPTO’s Patent Public Search tool lets you pull the full patent document, including filing date, grant date, and any PTA.6United States Patent and Trademark Office. Search for Patents From there, the Patent Maintenance Fees page shows whether each required payment was made.
Two dates control the math and they aren’t the same. The grant date sets the maintenance fee deadlines. The filing date sets the 20-year term. A patent filed in 2008 and granted in 2012 has a term expiring in 2028, but its first maintenance fee was due in 2015. If the owner missed that first fee, roughly 12 years of potential term is still on the table. If they missed the 11.5-year fee, you might be looking at only a year or two of enforceable life. Run both calculations before you make an offer.
Do the Due Diligence
Read the claims. A lapsed patent is only worth reinstating if its claims still read on something commercially useful. Broad claims covering technology that has become standard in an industry are valuable; narrow claims on a product design no one uses anymore are not.
Check for prior litigation and post-grant challenges. The Patent Trial and Appeal Board’s records and court databases like PACER show whether claims have already been narrowed or invalidated. If key claims were knocked out, reinstating won’t bring them back. Pull the file wrapper too, because heavy amendments during prosecution can signal that the surviving claims are vulnerable to future challenges.
Then confirm who actually owns the patent. Ownership may have moved through mergers, bankruptcies, or estates without being recorded. The USPTO’s Assignment Center shows recorded transfers but won’t catch unrecorded ones. You need clean chain of title, so a patent attorney is often worth the fee just to trace it.
Watch for Intervening Rights
This is the point most buyers underestimate. While the patent sat expired for nonpayment, anyone in the country could legally start making, using, or selling the invention. Reinstating the patent doesn’t automatically stop them.
Under 35 U.S.C. § 41(c)(2), anyone who began using the technology after the grace period ended and before the maintenance fee was accepted has a statutory right to continue that specific activity.3Office of the Law Revision Counsel. 35 USC 41 – Patent Fees; Patent and Trademark Search Systems A court can also allow continued manufacturing or process use where substantial preparation happened during the lapse. Terms and scope are set by the court based on what’s equitable.
The longer the patent has been down, the more likely competitors moved in. If you’re eyeing a patent that lapsed several years ago, investigate the market before you buy. Intervening rights reduce the value of what you’d be acquiring, and sometimes they gut it.
Negotiate and Record the Assignment
The current owner still holds title even though the patent isn’t currently enforceable, so you need a patent assignment agreement that transfers all rights, title, and interest to you. Price is between you and the seller; typical leverage points are the remaining term, the strength of the claims, and any intervening rights that already exist.
Once the assignment is signed, record it with the USPTO through the Assignment Center.7United States Patent and Trademark Office. MPEP 302 – Recording of Assignment Documents Upload a copy of the executed assignment (not the original) with a cover sheet listing the patent number, the parties’ names and addresses, the interest conveyed, and the execution date. If the assignment is in another language, include a signed English translation. Electronic recording is free; paper submissions cost $54 per patent.8USPTO. USPTO Fee Schedule – Current
Recording isn’t required to make the assignment valid between you and the seller, but it protects you against a later transfer by the same seller to someone else and puts your ownership in the public record before you file the reinstatement petition.
File the Petition To Reinstate
Reinstatement runs through 37 CFR 1.378. The Director will accept a delayed maintenance fee payment and reinstate the patent if the petition includes the overdue maintenance fee, the petition fee, and a statement that the delay in payment was unintentional.1eCFR. 37 CFR 1.378 – Acceptance of Delayed Payment of Maintenance Fee in Expired Patent To Reinstate Patent
ePetition, Within Two Years
If the patent has been expired for nonpayment for two years or less, the fastest path is the web-based ePetition process in Patent Center. The system can auto-process and decide the petition, sometimes on the same day.9United States Patent and Trademark Office. MPEP 2590 – Acceptance of Delayed Payment of Maintenance Fee in Expired Patent To Reinstate Patent Fees are paid electronically during the filing.
Paper Petition, Form PTO/SB/66
If ePetition isn’t available for your situation, file Form PTO/SB/66 through Patent Center.10U.S. Patent and Trademark Office. PTO/SB/66 – Petition To Accept Unintentionally Delayed Payment of Maintenance Fee in an Expired Patent The form asks for the patent number, the maintenance window that was missed, the statement of unintentional delay, and payment information. The Office of Petitions reviews these by hand, so decisions take longer.
Delays of More Than Two Years
The standard for reinstatement stays the same past the two-year mark, but the USPTO looks harder. Long gaps raise the question of whether the delay was truly unintentional, and the office may ask for a detailed explanation of the circumstances.11Federal Register. Clarification of the Practice for Requiring Additional Information in Petitions Filed in Patent Applications and Patents Based on Unintentional Delay The petition fee also moves to a higher tier. Be ready with a credible, specific account of why the fee went unpaid.
What Reinstatement Costs
The total is the overdue maintenance fee plus the petition fee. Maintenance fees as of March 2026:
- 3.5-year fee: $2,150 large entity, $860 small entity, $430 micro entity
- 7.5-year fee: $4,040 large entity, $1,616 small entity, $808 micro entity
- 11.5-year fee: $8,280 large entity, $3,312 small entity, $1,656 micro entity
Petition fee, based on how long the patent has been expired:8USPTO. USPTO Fee Schedule – Current
- Two years or less: $2,260 large entity, $904 small entity, $452 micro entity
- More than two years: $3,000 large entity, $1,200 small entity, $600 micro entity
A large entity reinstating a patent that missed the 11.5-year fee more than two years ago is looking at $11,280 in USPTO fees alone, before attorney costs and before whatever you paid the seller. A micro entity reinstating right after a missed 3.5-year fee could get in for $882. Work these numbers into what you offer the current owner.12United States Patent and Trademark Office. USPTO Fee Schedule
What You Actually Own After Reinstatement
If the petition is granted, the patent is treated as though it never expired.1eCFR. 37 CFR 1.378 – Acceptance of Delayed Payment of Maintenance Fee in Expired Patent To Reinstate Patent Enforceability comes back for whatever remains of the 20-year term plus any PTA. You can license, enforce, or hold defensively.
Two limits stay with you. Intervening rights still protect anyone who moved into the technology during the lapse. And future maintenance fees remain on the original schedule; if you reinstated at the 3.5-year window, the 7.5-year and 11.5-year fees are still due when they come around. Miss one, and you’re back where the seller started.
Denials are uncommon when the petition includes every required element, but they happen, particularly for very long delays. If you’re denied, you have two months to request reconsideration. If that fails too, the USPTO refunds the maintenance fee but keeps the petition fee.