You can wait years to sue, but you can only recover for the six years before you file. That six-year lookback applies to patent infringement, which means unauthorized making, using, or selling of a patented invention. Waiting does not create an automatic filing deadline. It shrinks what you can collect, because older acts fall outside recovery and other notice and fairness rules can cut further.
Table of Contents
- What does the six-year rule actually limit?
- Can delay alone wipe out timely damages?
- When can waiting still cost you the case?
- Why does marking change your start date?
- What should you check before you wait?
What does the six-year rule actually limit?
Federal law bars damages for infringement committed more than six years before the complaint or counterclaim was filed. The Cornell Legal Information Institute posts the text of 35 U.S.C. Section 286 with that six-year cutoff.
That rule limits recovery, not the right to file. Each separate infringing act starts its own clock, according to Klarquist's patent-defenses guide. So ongoing sales keep the case alive. A patentee who sues after long delay can still recover for the six years before suit, but cannot reach earlier sales.
Can delay alone wipe out timely damages?
No. Delay alone does not bar damages for infringement inside the six-year window. The Supreme Court decided that issue 7-1 in SCA Hygiene v. First Quality in 2017.
The Court held that laches cannot defeat a damages claim brought within the Section 286 period. A Staas and Halsey summary explains the SCA Hygiene ruling on laches and its effect on patent damages. That protection applies to past money damages. It does not give the patentee the same protection for forward-looking court orders.
When can waiting still cost you the case?
One defense survived SCA Hygiene: equitable estoppel. Fenwick and West explains that estoppel can completely bar enforcement when three things line up. The accused infringer must show misleading conduct by the patentee, reasonable reliance on it, and material prejudice.
Silence alone is rarely enough, while a false assurance followed by business investment is the classic risk. Delay can also cost forward-looking relief. Analysis from Koffsky Schwalb notes that laches remains available against equitable relief such as injunctions, so a slow patentee may keep past damages but lose an order stopping future infringement.
Why does marking change your start date?
A second timing rule comes from marking. Under 35 U.S.C. Section 287, a patentee that makes or sells patented articles generally must mark them with the patent number.
If the patentee fails to mark, damages usually start only after the infringer gets actual notice and keeps infringing. A Fish and Richardson analysis describes the marking and pre-suit damages rule and how compliance affects recovery. The practical result is a shorter pay period. Unmarked sales before notice yield no damages, even when they fall inside the six-year window.
What should you check before you wait?
First, check expiration. An expired patent can still support suit for past harm if filed within six years after expiration, with recovery limited to pre-expiration acts inside the window, as discussed in an Oblon review of suits on expired and disclaimed claims. Second, protect the value of any claim you may bring: Each month of delay can move older sales outside Section 286 and create disputes over notice and reliance.
- Write down when you first saw each infringing product and save dated proof.
- Check whether your products were marked, and send clear written notice promptly.
- Avoid statements that could look like permission or abandonment.
- Get legal advice before relying on continued sales to preserve recovery.