Find a patent's priority date and the applications it comes from
The priority date is the date a patent's claims are entitled to, usually the filing date of the earliest application it validly claims priority from. It decides which earlier documents count as prior art against it. The relevant dates and application numbers sit on the front page and in the related applications text. Ask Search+ "What priority does this patent claim, and from which applications?" and open the citation to read them.
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Last updated October 2026
How to find a priority date with Search+
- Upload the patent and its family members
Add the patent. If you have the earlier applications it claims priority from, add them too, even as scans, so you can ask what each one disclosed.
- Ask for every date and application number
Ask for the priority claims, the filing date and the publication date as separate items. Patents carry several dates, and keeping them apart avoids confusion.
- Check what the earlier application disclosed
Priority generally only covers subject matter disclosed in the earlier application. Ask whether a claimed feature appears in the priority document, and read the citations from both.
Questions to ask about priority dates
Which earlier applications does this patent claim priority to, and with what dates?
What are the filing date, priority date and publication date of this patent?
Does the patent describe itself as a continuation or divisional of an earlier application?
Does the earlier application in this workspace describe the feature claimed in claim 3?
Across the patents in this workspace, which ones claim the same earliest priority application?
What to look for around a priority date
A patent shows filing, priority, publication and grant dates. The priority date is the one that matters for deciding which earlier disclosures are prior art.
Claims are generally entitled to an earlier priority date only for subject matter that the earlier application disclosed. Different claims in one patent can have different effective dates.
Under the Paris Convention, an applicant can claim priority from a first application when filing in other member countries within a set period (12 months for patent applications). The front page lists those foreign priority claims.
Divisionals, and in US practice continuations, state their relationship to earlier applications, usually near the start of the description.
Answers cite the front-page or description passage they came from, and Search+ does not invent locations the patent does not contain.
Put both documents in one workspace and ask across them, or ask about one alone.
Date wording and what to ask next
Most labels below are as printed on US patents; other offices use similar but not identical headings.
| Wording you may see | What it usually signals | A follow-up question |
|---|---|---|
| "Foreign Application Priority Data" | Priority claimed from a filing in another country | Which country and date are listed? |
| "Related U.S. Application Data" or similar | Earlier applications in the same family | Is this patent a continuation or a divisional? |
| "provisional application" | In US practice, an earlier provisional filing that is not examined and can be relied on for priority | What date was the provisional filed? |
| "claims the benefit of" | A priority or benefit claim | Which application does it claim the benefit of? |
| "Filed:" | The filing date of this application | How does the filing date differ from the priority date? |
| "continuation-in-part" | In US practice, a later application that adds new matter to an earlier one | Which parts are new compared with the parent? |
What is a priority date in a patent?
A priority date is the date a patent's claims are entitled to for judging what counts as prior art, generally the filing date of the earliest application from which the patent validly claims priority for that subject matter.
Priority date questions
Can Search+ find a patent's priority date?
Can it tell which claims are entitled to the earlier date?
Can it explain the patent's family relationships?
Is this legal advice about patent dates?
What if the earlier application is a scanned image?
Can an answer mix up the dates?
Get the dates right before anything else
Start a workspace, upload the patent and its family, and ask what priority it claims.
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