Your patent attorney tells you a “terminal disclaimer” is needed to overcome an examiner’s rejection. You sign off on it without much thought—it sounds routine. But that simple filing can have significant implications for your patent portfolio that you should understand before agreeing.

Here’s what terminal disclaimers actually do, when they make sense, and what you’re giving up when you file one.

The Problem Terminal Disclaimers Solve

Patent law has a fundamental rule: you can’t get two patents on the same invention. This prevents a patent owner from effectively extending their monopoly beyond the standard 20-year term by filing a second patent on the same thing just before the first one expires.

But what counts as “the same invention”? That’s where things get complicated—and where two different types of double patenting come into play.

Two Types of Double Patenting

Statutory Double Patenting occurs when claims in two patents or applications are identical or essentially identical. This directly violates 35 U.S.C. § 101’s requirement that a patent be granted for “an invention”—singular. You simply cannot have two patents claiming the exact same thing.

Obviousness-Type Double Patenting (ODP)—also called non-statutory double patenting—occurs when claims aren’t identical but are obvious variations of each other. This is a judicially created doctrine designed to prevent patent owners from extending their exclusivity by filing continuation applications with minor tweaks to the claims.

How Obviousness-Type Double Patenting Works

If you file a continuation application (or any application with the same priority date as an existing patent), the examiner will compare your new claims to your existing patent’s claims. If the new claims are “patentably indistinct”—meaning they’re obvious variations of what you already patented—the examiner will reject them under ODP.

This isn’t the same as a regular obviousness rejection under 35 U.S.C. § 103. ODP compares your new claims to your own earlier patent, not to prior art. The question isn’t whether your invention is obvious over what existed before—it’s whether your new claims are just a minor tweak of claims you already own.

Type	Problem	Solution
Statutory Double Patenting	Claims are identical	Must amend or cancel duplicate claims
Obviousness-Type Double Patenting	Claims are obvious variations	Terminal disclaimer can overcome

What a Terminal Disclaimer Does

A terminal disclaimer is the standard way to overcome an obviousness-type double patenting rejection. (Remember: it cannot overcome statutory double patenting where claims are identical.) When you file one, you’re agreeing to two things:

1. Term Alignment

You disclaim any portion of your new patent’s term that extends beyond the expiration date of the reference patent. If Patent A expires on January 1, 2030, and Patent B would otherwise expire on March 15, 2035, the terminal disclaimer cuts Patent B’s term short—it now expires on January 1, 2030 too.

2. Common Ownership Requirement

You agree that the new patent is only enforceable while it’s commonly owned with the reference patent. If you sell or license one patent without the other, the patent subject to the terminal disclaimer becomes unenforceable.

When Terminal Disclaimers Make Sense

Terminal disclaimers aren’t inherently bad—they’re a tool. Used strategically, they can strengthen your patent portfolio.

Building Claim Diversity

Sometimes having multiple patents with different claim sets is more valuable than a single patent with many claims. If a competitor designs around your original claims, your continuation with slightly different claims might still catch them. A terminal disclaimer lets you get that second patent issued.

Correcting Prosecution Mistakes

If your original patent’s claims were drafted too narrowly, a continuation with broader claims (and a terminal disclaimer) can expand your protection. Yes, the two patents will expire together, but you’ll have broader coverage during that time.

Covering Different Embodiments

Your product may have evolved since your original filing. A continuation application can capture those improvements. If the examiner sees ODP issues, a terminal disclaimer gets the patent issued so you have coverage for what you’re actually selling now.

The Hidden Costs of Terminal Disclaimers

Before automatically agreeing to file a terminal disclaimer, understand what you’re giving up.

Lost Patent Term

If your reference patent has less remaining term than your new application would have, the terminal disclaimer shortens your protection. This matters especially when:

• Your original patent received little or no patent term adjustment (PTA)
• Your continuation has significant PTA due to USPTO delays
• There’s a gap of several years between your filing dates

You could be giving up months or years of patent protection.

Licensing and Assignment Complications

The common ownership requirement creates friction in deals. If you want to sell part of your portfolio, or grant exclusive licenses to different parties for different patents, terminal disclaimers can block or complicate those transactions.

Enforcement Complexity

In litigation, terminally disclaimed patents are linked. While current law evaluates validity claim-by-claim, opponents will argue (and courts may consider) that invalidating claims in one patent should affect the linked patent. This gives defendants additional attack vectors.

The 2024 Proposed Rule: A Close Call

In May 2024, the USPTO proposed a dramatic change to terminal disclaimer practice. Under the proposed rule, if you filed a terminal disclaimer, your patent would become unenforceable if any claim in the reference patent was ever found invalid or unpatentable.

This would have been devastating for patent portfolios. Invalidate one claim in one patent, and every patent linked by terminal disclaimers falls with it. The proposal drew fierce opposition from the patent bar, including a letter from five former USPTO directors urging withdrawal.

The USPTO withdrew the proposed rule in December 2024, citing resource constraints and the volume of critical comments received. But the fact that the rule was proposed at all signals ongoing scrutiny of terminal disclaimer practice—and the possibility of future changes.

Strategic Alternatives to Terminal Disclaimers

Before reflexively filing a terminal disclaimer, consider whether alternatives exist.

Argue Against the Rejection

ODP rejections require the examiner to show your new claims are obvious variations of your existing claims. This isn’t always a slam-dunk analysis. If the claims are meaningfully different—different scope, different elements, different applications—you may be able to overcome the rejection through argument alone.

Amend the Claims

Sometimes narrowing or refocusing your continuation claims eliminates the ODP issue. Yes, you get narrower claims, but you avoid the terminal disclaimer’s baggage.

Pursue a Restriction Requirement

If your application contains claims to genuinely distinct inventions, you may be able to obtain a restriction requirement from the examiner. Divisional applications filed in response to restriction requirements are generally immune from ODP rejections—the examiner already acknowledged the inventions are distinct.

Accept the Rejection

Sometimes the right answer is not to pursue the continuation at all. If the new claims don’t add significant value over what you already have, the costs of a terminal disclaimer may outweigh the benefits of another patent.

Questions to Ask Before Filing a Terminal Disclaimer

When your attorney recommends a terminal disclaimer, ask:

• How much term am I losing? Compare the expiration dates of both patents, accounting for any PTA.
• Do I anticipate selling or licensing these patents separately? If so, the common ownership requirement could be a problem.
• Can we argue against the ODP rejection instead? Not all ODP rejections are well-founded.
• What’s the incremental value of this patent? If the new claims don’t add meaningful protection beyond what you already have, is another patent worth the complications?
• How many patents are already linked? Each additional terminal disclaimer increases your portfolio’s interconnected risk.

Managing a Portfolio with Terminal Disclaimers

If you already have patents linked by terminal disclaimers, or if filing one is the right strategic choice, keep these principles in mind.

Track Your Linkages

Maintain a clear map of which patents are tied together. In a large portfolio, these relationships can become tangled. You need to know, before any licensing negotiation or enforcement decision, which patents come as a package.

Consider Enforcement Implications

If you’re asserting a terminally disclaimed patent, understand that the linked patent may become relevant to the litigation—even if you didn’t assert it. Defendants may seek to invalidate the reference patent as a strategy to weaken your position.

Be Thoughtful About Future Continuations

Each continuation application creates another potential ODP issue. Before filing, consider whether the new claims are worth potentially adding another link in your terminal disclaimer chain.

The Bottom Line

Terminal disclaimers are a routine part of patent prosecution, but “routine” doesn’t mean “insignificant.” Every terminal disclaimer trades patent term and portfolio flexibility for the ability to get additional claims issued.

Sometimes that trade makes sense. A diverse portfolio with multiple claim sets can be more valuable than a single patent, even if the patents expire together. But the decision should be deliberate, not automatic.

Before signing off on a terminal disclaimer, understand what you’re agreeing to—and make sure the benefits outweigh the costs for your specific situation.