What Section 15 Incontestability Actually Forecloses, and What Survives It

A client asks whether their incontestable registration means the mark can no longer be challenged. The honest answer is narrower than the label suggests. Incontestability under Section 15 does one thing with real force: it takes the mere descriptiveness challenge off the table. An incontestable mark cannot be attacked on the ground that it was descriptive and lacked secondary meaning when it registered. That is the holding of Park 'N Fly, Inc. v. Dollar Park and Fly, Inc., 469 U.S. 189 (1985), and it is the reason the affidavit is worth filing. Everything else about the "incontestable" label is oversold. Nine statutory defenses survive it, genericness can still sink the registration, and the window to claim it is wider than most firms use.

What Section 15 is, and what it is not

Section 15 of the Lanham Act, 15 U.S.C. § 1065, lets the owner of a mark registered on the Principal Register declare that the right to use the mark has become incontestable. It is optional. It is not the same filing as the Section 8 declaration of continued use, which is mandatory to keep the registration alive. The two are commonly filed together as a combined Sections 8 and 15 declaration between the fifth and sixth years after registration, and that habit is part of why the distinction blurs. TMEP § 1605 governs the Section 15 affidavit.

Four conditions must hold before incontestability attaches under § 1065:

• Five consecutive years of continuous use. The mark has been in continuous use in commerce for five consecutive years after registration and is still in use.
• No adverse final decision. There has been no final decision adverse to the owner's claim of ownership or right to register the mark.
• No pending challenge. No proceeding involving those rights is pending in the Office or in the courts.
• The mark is not generic. A generic mark cannot become incontestable, and it cannot stay registered.

Meet those, file the affidavit within the window, and the registration converts under 15 U.S.C. § 1115(b) from prima facie evidence of the owner's exclusive right to use the mark into conclusive evidence of it. That word, conclusive, is the whole prize. It is also where the overreading starts.

The one thing it forecloses: the descriptiveness attack

Before incontestability, a defendant in an infringement suit can argue that the plaintiff's registered mark was merely descriptive and never acquired secondary meaning, and therefore should not have registered at all. That defense is available against an ordinary registration under Section 33(a). Incontestability closes it.

In Park 'N Fly, the Supreme Court held that the holder of an incontestable mark may enjoin infringement, and the alleged infringer may not defend by claiming the mark is merely descriptive. Congress listed the defenses that survive incontestability in Section 33(b), and descriptiveness is not among them. A term that was arguably weak at registration, "Park 'N Fly" for airport parking being the case in point, becomes conclusively valid on that ground once the affidavit is filed and accepted.

This is the concrete value. For descriptive marks and marks that registered on a showing of acquired distinctiveness, incontestability retires the single most common validity attack a defendant will reach for. For an inherently distinctive mark that was never vulnerable to a descriptiveness argument, the practical gain is smaller, which is worth knowing before you tell a client the filing changed their position.

The nine defenses that survive

Section 33(b), 15 U.S.C. § 1115(b), makes the incontestable registration conclusive evidence of validity, ownership, and the exclusive right to use, and then lists nine defenses that remain available. An incontestable registration is not immune. A defendant can still raise:

1. Fraud in obtaining the registration or the incontestable right.
2. Abandonment of the mark by the registrant.
3. Use to misrepresent the source of the goods or services.
4. Fair use, where the term is used descriptively and in good faith, otherwise than as a mark.
5. Prior use by the defendant, adopted without knowledge of the registrant's earlier use and continued in a limited geographic area.
6. Prior registration and use by the defendant that predates the registrant's rights.
7. Use to violate the antitrust laws of the United States.
8. Functionality, where the mark is or has become functional.
9. Equitable principles, including laches, estoppel, and acquiescence.

Two of these deserve emphasis because they are the ones clients assume incontestability solves. Abandonment survives. Three consecutive years of nonuse is prima facie abandonment under 15 U.S.C. § 1127, and an incontestable registration offers no shield against it. Functionality survives, which matters for any mark that carries product-configuration or trade-dress weight. And genericness sits outside the list entirely: under 15 U.S.C. § 1064(3), a registration can be cancelled at any time if the mark becomes the generic name for the goods or services, incontestable or not. The label describes the mark's status, not its immortality.

The window most firms misread

Here is the point that changes practice. The Section 15 affidavit is not a one-shot filing tied to the first Section 8. Under § 1065, the affidavit is filed within one year after the expiration of any five-year period of continuous use. Not the first such period. Any of them.

The five-and-six-year custom exists because the mandatory Section 8 declaration falls in that window, so combining the two is efficient. But a registrant who lets the first window pass, or who could not claim incontestability then because a proceeding was pending, is not locked out. Once five more consecutive years of continuous use accrue with no adverse decision and no pending challenge, a fresh one-year window opens and the affidavit can be filed against that later period.

That reframes two situations firms tend to write off:

• The missed first window. A registration that reached year six without a Section 15 filing has not forfeited incontestability. It waits for the next clean five-year run.
• The mark that was in litigation. A pending opposition, cancellation, or infringement suit blocks incontestability while it is live, because § 1065 requires that no proceeding be pending. When the dispute resolves in the owner's favor and five consecutive years of continuous use are on the record, the door reopens.

The requirement to watch is the "no pending proceeding" and "no adverse final decision" condition. Filing a Section 15 affidavit while a challenge is live, or after a decision that went against the owner's claim, is filing a defective declaration. Confirming the mark's clean record before you file is not paperwork. It is the substance of the eligibility.

That record check is register work. Confirming there is no pending proceeding and no adverse decision touching the mark, across the Office and the courts, is exactly the kind of continuous read of the public record that Redrift keeps current, so counsel can see the mark is clean before the affidavit goes out. The fabric surfaces the record. Whether the mark is eligible, and whether incontestability is worth claiming at all, stays with the lawyer.

What to do with this

Treat incontestability as a specific tool, not a status upgrade. For a descriptive mark or one registered under Section 2(f), file the Section 15 affidavit as soon as a clean five-year period closes, because it retires the descriptiveness defense a future infringer would otherwise raise. For an inherently strong mark, recognize that the filing buys less and calendar it accordingly. When advising a client who believes an incontestable registration cannot be touched, name the nine defenses and the genericness exception before they build a strategy on a false floor. And when a first window was missed or a proceeding blocked it, do not treat the option as gone. Watch for the next clean five-year period and the fresh window it opens.