What is the prohibition of nonstatutory double patenting rejections under 35 U.S.C. 121?

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.

The prohibition of nonstatutory double patenting rejections under 35 U.S.C. 121 is a legal provision that prevents the use of a patent issuing from an application with a restriction requirement as a reference against a divisional application in a nonstatutory double patenting rejection. This protection applies only when:

• The Office has made a requirement for restriction
• The divisional application is filed before the issuance of the patent
• The claims in the divisional application are consonant with the restriction requirement

As stated in the MPEP, “The 35 U.S.C. 121 prohibition applies only where the Office has made a requirement for restriction. The prohibition does not apply where the divisional application was voluntarily filed by the applicant and not in response to an Office requirement for restriction.“