What are the time limits for responding to a notice under 37 CFR 1.251?

The time limits for responding to a notice under 37 CFR 1.251 vary depending on whether it’s for an application or a patent:

• For applications: The Office sets a three-month period for reply, which is extendable under 37 CFR 1.136(a) by up to three additional months, for a maximum of six months.
• For patents: The Office sets a six-month period for reply, which is not extendable.

MPEP 508.04 states: “The Office will set a time period of three months for reply in a notice under 37 CFR 1.251 in an application. The time period will be extendable under 37 CFR 1.136(a) (unless the notice indicates otherwise) by three months up to a maximum period for reply of six months in an application.” It also notes: “The Office will set a time period of six months for reply in a notice under 37 CFR 1.251 in a patent. The time period will not be extendable under 37 CFR 1.136(a) in a patent.”