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What the Twelve Months Actually Buy

Written from 35 U.S.C. 119(e). This is the statute. Current as of 22 August 2026.

What it says

A provisional on its own expires and confers nothing. Section 119(e) treats a later application as though filed on the provisional's date as to such invention, if the provisional disclosed it the way section 112(a) requires apart from best mode, and if the timing and reference conditions are met. Entitlement runs claim by claim, not application-wide.

This is the section that makes a provisional worth filing, and it is not the section most people read.

The benefit is conditional on three things, and each can fail independently.

The disclosure has to carry the invention. The later application gets the earlier date only for an invention the provisional disclosed in the manner provided by section 112(a). A provisional that describes something narrower than what you later claim does not carry the later claim.

The later application must be filed within twelve months, subject to a two-month extension where the delay was unintentional.

It must contain a specific reference to the provisional. The statute says the Director may consider a late reference a waiver, and separately authorises accepting an unintentionally delayed one, so this is discretionary rather than automatic.

The entitlement is invention-specific, and this is the part most explanations get wrong. The statute gives the later application the earlier date "as to such invention", meaning the invention the provisional disclosed. It does not hand a date to an application wholesale.

So a single application can hold claims with different effective filing dates. A claim the provisional fully supports can take the earlier date while a claim resting on something added later takes the later one. What does not happen is a claim splitting the difference: the claimed invention as a whole has to be supported for that claim to get the earlier date.

The practical consequence for the year is that the question is never simply "did we file in time." It is which parts of what you now want to claim were actually in the document you filed.

What This Does Not Decide

Whether your later application is entitled to your provisional's date is the question, and this page cannot answer it. The comparison looks mechanical, which is what makes it dangerous. It is a comparison between what a document disclosed and what a claim now covers, and that is the same judgment that decides written description cases.
  • It does not say whether any provisional supports any later claim. That is the whole question, and it is asked claim by claim.
  • It does not tell you when to file, or advise on the extension.
  • The two-month extension is a narrow softening for unintentional delay, not a fourteen-month window.

Educational, not legal advice. Filing decisions and benefit claims carry deadlines that do not reopen, which is the practical reason to take them to a registered patent practitioner early.

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