A priority claim is one of the cheapest things in a filing to get right and one of the more expensive things to fix. Put the right parent, provisional or foreign application in the ADS on time and it costs nothing. Miss the window, and the only way back is a petition.
The window
A claim to the benefit of an earlier U.S. application, or to priority from a foreign one, has to be made in the application data sheet within a fixed window: the later of four months from the filing date or sixteen months from the filing date of the earlier application (37 CFR 1.78 for domestic benefit, 37 CFR 1.55 for foreign priority). Inside that window, adding or correcting the claim is routine paperwork. Outside it, the claim can only be accepted on a petition showing the delay was unintentional.
What the fix costs
The petition needs three things: the claim itself, presented in a corrected ADS; a statement that the entire delay was unintentional; and the petition fee under 37 CFR 1.17(m), currently $2,260 for a large entity. For a claim to an earlier nonprovisional application, the continuing application fee under 1.17(w) can apply on top of that.
Since 13 August 2026 the rule is stricter. A petition filed more than one year after the deadline (previously two years) carries the higher fee of $3,000 and has to explain the whole period of delay, not just state that it was unintentional.
What the USPTO's own data shows
The USPTO's Petition Decisions dataset, on its Open Data Portal, now includes granted and dismissed decisions as well as denials, which makes routine petitions like these visible for the first time.
It is common. About 2,000 petitions to accept a late priority or benefit claim were decided in 2025, and the number has been in the thousands every year for the past decade.
It is not one kind of firm. Over the last three years these petitions came from more than a thousand different USPTO customer numbers, and the busiest single filer accounts for less than one percent of them. About 40% were filed by small or micro entities.
The fix often fails the first time. About four in ten decisions are dismissals. A dismissal means a renewed petition and another wait, usually over paperwork rather than substance. We looked at why late priority petitions get dismissed.
Where it starts
Almost every late claim starts on filing day. A provisional or parent left out of the chain. An application number typed with a digit missing or two digits swapped. A continuation entered as a continuation-in-part, or a national stage entered as a continuation. Each looks fine on a quick read, and by the time the filing receipt shows the problem, the window may already be closing.
Getting it right at filing
IPPrep Pro builds the priority chain from USPTO data when you enter the parent application number, then checks every claim in the ADS against the Office's own records before you file: that each number is in the right format, that each link in the chain matches what the USPTO has on file, and that the relationship (continuation, divisional, national stage, provisional) is the right one. It also tells you whether the continuing application fee applies, and sends reminders as the filing deadline approaches. See how the filing package works.
The cheapest petition is the one you never have to file.
Figures come from the USPTO Petition Decisions data on the Open Data Portal (decisions through October 2026); fees are the USPTO's large-entity amounts. This article is general information about USPTO practice, not legal advice. Confirm current rules and fees against the MPEP and the USPTO fee schedule for any specific matter.