How can a 37 CFR 1.131 affidavit affect the on-sale bar determination?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

A 37 CFR 1.131 affidavit, commonly used to swear behind a reference, can inadvertently affect the on-sale bar determination. The MPEP warns:

Affidavits or declarations submitted under 37 CFR 1.131 to swear behind a reference may constitute, among other things, an admission that an invention was “complete” more than 1 year before the filing of an application. (MPEP 2133.03(c))

This means that while trying to overcome a prior art reference, an inventor might inadvertently admit to having a complete invention more than one year before the filing date, potentially triggering the on-sale bar. Inventors and patent practitioners should be cautious when preparing such affidavits to avoid unintended consequences.