Strategic Timing
Most practitioners treat "6 months after publication" as the rule. For any application claiming an earlier priority date — domestic or PCT — it's usually a floor, not a ceiling.
The window closes at the later of 6 months post-publication or the first Office Action. Because publication runs from the earliest priority date while examination runs from the actual US filing date, any priority-claiming application usually gets a window that extends all the way to the first OA — for PCT-origin cases, often 4+ years from priority. The one thing that ends it early, always, is a Notice of Allowance.
The "Later Of" Clause Does the Heavy Lifting
Recall the rule from the calculator: absent a Notice of Allowance, the window stays open until the later of (a) 6 months after publication, or (b) the date of the first rejection of any claim. The 6-month prong only controls when the first Office Action arrives within those 6 months. Whenever examination lags publication by more than 6 months — which, as the numbers below show, is the norm rather than the exception for priority-claiming applications — the deadline is simply the first Office Action date, whenever that turns out to be.
Two practical consequences follow. First, silence is not a deadline: an application that is past the 6-month mark with no OA on the record is still open. Second, the window has no fixed end date in that state — it closes on the day the first OA mails, with no grace period after.
Where the First Office Action Actually Lands
Publication under 35 U.S.C. § 122(b) happens at 18 months from the earliest priority date. First-action pendency — filing date to first Office Action — has recently averaged:
| Fiscal Year | Avg. First-Action Pendency |
|---|---|
| FY 2024 | 19.9 months |
| FY 2025 | 22.6 months |
| FY 2026 (year to date) | 21.0 months |
For an application with no earlier priority claim, both clocks start on the same day: publication at month 18, window floor at month 24, first OA on average around months 20–23. The average first OA therefore lands somewhere between a third and three-quarters of the way through the 6-month window — meaning the 6-month prong usually controls, and the window genuinely is about 6 months long. That is the case the "6-month rule" folklore describes.
But that case is the exception in modern practice, because most serious applications claim earlier priority.
The Priority-Claim Effect
The two clocks start from different dates. Publication runs from the earliest priority date; examination pendency runs from the actual non-provisional filing date. Every month of priority claimed is a month of examination delay relative to publication.
Take the most common domestic pattern — a provisional converted at the 12-month deadline:
| Event | Months from priority date |
|---|---|
| Provisional filed (priority date) | 0 |
| Non-provisional filed | ~12 |
| Publication (18 months from priority) | ~18 |
| 6-month prong closes | ~24 |
| Average first Office Action (~20–22 months from filing) | ~32–34 |
The first OA lands roughly 8–10 months after the 6-month prong has passed — so the "later of" clause takes over and the window runs all the way to the first Office Action. A filer who assumed the window closed at month 24 walked away from an extra ¾ of a year, and often more. The same logic applies to applications claiming foreign priority under the Paris Convention.
The PCT Window: The Biggest and Least Known
For PCT-origin applications the effect is dramatic. Under 35 U.S.C. § 374, WIPO's international publication of a PCT application designating the US is deemed the § 122(b) publication. That happens around 18 months from priority — but the application typically doesn't enter the US national phase until 30–31 months from priority, and only then joins the examination queue with its own ~20–22 month wait to a first OA.
| Event | Months from priority date |
|---|---|
| PCT filing / priority date | 0 |
| WIPO international publication (deemed § 122(b) publication) | ~18 |
| 6-month prong closes | ~24 |
| US national phase entry | ~30–31 |
| Average first Office Action | ~50+ |
The 6-month prong closes before the case has even entered US prosecution — so it is almost never what controls. The real deadline is the first Office Action, which for PCT-origin applications routinely lands 4+ years after the priority date. If you found prior art against a PCT-origin application and assumed you missed the window at month 24, you very likely didn't.
None of this softens the hard stop: a Notice of Allowance closes the window immediately, whenever it comes. Accelerated cases (Track One, PPH) can compress the entire timeline and even reach allowance before you expect any examination activity. A long expected window is a reason to file well, not a reason to wait. Verify the file wrapper before relying on any of these averages.
When Within the Window Should You File?
An open window poses a second question: file now, or wait? Both positions have real advantages.
| Filing before the first OA | Filing after an early first OA | |
|---|---|---|
| What you're doing | Getting art in front of the Examiner before their first search and before the Applicant's arguments crystallize. | Targeting art at the claims as amended, or at the specific arguments the Applicant made in response. |
| Best when | Your art reads on the claims as filed; you want it baked into the first rejection. | The first OA revealed how the Applicant will narrow, and you hold art that reads on the narrowed claims. |
| Main risk | Applicant amends around your art early, with maximum room to maneuver (see Strategic Risks). | The window may close before you file: an NOA can follow a response at any time, and this position only exists at all when no 6-month cushion remains. |
Be careful about which state you're in. The post-OA opportunity only exists when the first OA arrives within 6 months of publication — the window then continues to the 6-month mark, so you can see the rejection (and sometimes the Applicant's response) before filing. In the extended-window state — past the 6-month mark with no OA yet — "waiting for the first OA to see the Examiner's position" is not an option: the window closes the day that OA mails. The practical strategy there is to prepare the submission fully and file before examination begins.
Check where your target application sits with the Deadline Calculator, and weigh whether to file at all with the decision framework.