What is a Terminal Disclaimer?

Key Facts

• Rule: 37 C.F.R. § 1.321(c) and (d); practice in MPEP § 804.02 and § 1490
• Purpose: Overcome a non-statutory (obviousness-type) double patenting rejection over a commonly owned patent or application
• Effect on term: The later patent expires no later than the reference patent; any patent term adjustment beyond that date is lost
• Common ownership requirement: The patent is enforceable only while it and the reference patent are owned by the same entity
• Permanence: A disclaimer recorded in an issued patent cannot be withdrawn, though one filed in a pending application can be withdrawn before issue
• Fee: A modest USPTO fee per disclaimer

Why Double Patenting Exists

An applicant is not allowed two patents with claims that are the same or obvious variants of one another, because the second would unjustifiably extend exclusivity past the first and would let the two patents be split between owners and asserted separately. Statutory double patenting (identical claims) cannot be cured by disclaimer. Obviousness-type double patenting, where the claims are merely obvious over each other, can be.

The rejection is most common between a parent and its continuation, or between siblings in the same family. Divisionals filed after a restriction requirement are shielded by the § 121 safe harbor and should not receive the rejection.

What the Applicant Gives Up

1. Term: Where both patents share a priority date and neither has meaningful term adjustment, the disclaimed term is often zero or a few days. Where the reference patent expires earlier, or the later patent has large PTA, the loss can be years.
2. Separability: The patents cannot be sold or exclusively licensed apart from each other. This matters in M&A and in monetization programs that carve portfolios by product line.
3. Enforceability risk: If common ownership lapses, for example through a partial assignment, the disclaimed patent becomes unenforceable until ownership is realigned.

Alternatives to Filing One

• Argue the rejection: Show the claims are patentably distinct, which preserves full term
• Amend the claims: Add a limitation the reference patent does not suggest
• Cancel the claims: Drop the overlapping claims and rely on the reference patent
• Accept it: When the disclaimed term is negligible and common ownership is certain, filing is usually the fastest route to allowance

In 2024 the USPTO proposed, and then withdrew, a rule that would have made a terminally disclaimed patent unenforceable if any claim of the reference patent was held invalid. The withdrawal left the traditional rules above in place. Because terminal disclaimers silently cap term across a family, portfolio management systems should record them on every affected asset so expiration dates and licensing terms are computed correctly.