Failing to Spot a PTO Printing Error Could Cost You

July 11, 2014

Eric Rutt

What This Means to You

  • Review your patents for PTO printing errors at the time they issue.
  • If you discover a printing error in your patent shortly after it issues, seek a certificate of correction immediately.
  • If you only discover a printing error after infringing conduct has begun, you may be at risk of losing patent damages unless the error is a harmless typo evident on the face of the patent.


H-W Technology, L.C. v., Inc., a recent decision in the U.S. Court of Appeals for the Federal Circuit (Federal Circuit), illustrates the importance of finding and fixing errors in your patent as soon as possible after issuance.

Case Background

In April 2009, a patent was issued to H-W Technology, L.C. for a phone capable of making purchases over a data network without making a voice call. H-W sued for patent infringement in March 2012. Later that year, Overstock notified H-W that the U.S. Patent and Trademark Office (PTO) had failed to print an entire limitation in claim 9 of the patent. In May 2013, H-W obtained from the PTO a certificate of correction that added the missing limitation. However, H-W did not supplement its pleadings with the district court to assert the corrected claim. The district court granted summary judgment, holding that the court could not correct the error in claim 9, and that the claim was indefinite.

Decision Analysis

The Federal Circuit affirmed the district court’s holding that it could not correct claim 9, but clarified that the corrected version of claim 9 was not part of the lawsuit because H-W had not asserted it. For that reason, the Federal Circuit removed from the judgment the holding that corrected claim 9 was invalid.

Although H-W obtained a certificate of correction, it did not assert the corrected claim. Instead, H-W argued that the district court could correct the error. However, a district court can only correct a PTO printing error if, among other things, the error is evident from the face of the patent. In this case, nothing on the face of the patent indicated the uncorrected claim contained an error. The error was evident from the prosecution history, but that alone is not sufficient to allow the district court to correct the error. The Federal Circuit held it would be inequitable to allow H-W to assert the uncorrected claim because such a rule would allow patent owners to assert claims they never asked for nor rightly obtained.

H-W’s decision not to assert its corrected claim highlights a dilemma that confronts patent owners who discover errors late in the game. A certificate of correction is only effective as to causes of action arising after the date the certificate issued. Patent owners thus cannot recover damages that accrued before the certificate issued.

In sum, if a district court can correct a PTO printing error, a patent owner can seek pre-correction damages; but if the error requires a PTO certificate of correction (if the error is not evident from the face of the patent), then the patent owner loses pre-correction damages. Where, as here, the district court cannot correct the error, the patent owner loses damages for any pre-correction infringement. To avoid that outcome, H-W apparently tried to have it both ways: After obtaining a certificate of correction, it argued the certificate was not needed. The Federal Circuit did not buy it.


Patent owners can avoid losing the right to recover damages for patent infringement by identifying and correcting PTO printing errors as soon as their patents issue. If an error is only discovered after the incorrect patent has been asserted in litigation, patent owners may still be able to avoid losing damages if the error is of the type that can be corrected by the district court.