How to Estimate a Regulatory Submission Timeline

Ask when a submission will clear review, and the honest answer starts with a disclaimer: the number a stakeholder wants is a calendar date, and the number FDA actually publishes is a count of its own working days. Confusing those two is not a technicality — it is the single most common way a regulatory timeline promise turns into a bad one. Reading FDA’s review clock correctly, and knowing exactly when it stops counting against the agency and starts counting against you, is what separates a defensible internal date from a guess dressed up as a plan.

In brief

A PMA carries a genuine statutory decision period — 180 days from the date of filing, under 21 CFR § 814.40 — though FDA may take longer once an advisory committee is convened or the applicant submits a major amendment, which resets the clock under § 814.37.
A 510(k) has no equivalent statute-set deadline. Its familiar “90 days” comes from FDA’s negotiated performance goals under the Medical Device User Fee Amendments (MDUFA), published in the agency’s performance goals and procedures letter for each five-year user-fee cycle — not from the Federal Food, Drug, and Cosmetic Act itself.
Both clocks stop, not just pause, the moment FDA places a file on hold for an Additional Information request (510(k)) or sends a major deficiency or approvable letter (PMA). The clock resumes only once FDA receives a complete response — the time spent drafting that response is not counted against FDA’s side of the ledger.
The biggest driver of total calendar time to a decision usually is not FDA’s active review days at all. It is how many hold-and-respond rounds a submission goes through, and how long each response takes your own team to prepare.

Two clocks, not one

Start by being precise about which clock a given submission is actually running on, because the two mechanisms work differently enough that treating them as interchangeable will eventually embarrass you in front of a stakeholder. A PMA’s 180-day period is a real statutory commitment under section 515(d) of the FDCA, codified at 21 CFR § 814.40: it runs from the date of filing — not the date of receipt, which FDA confirms separately within 45 days — and it obligates FDA to issue an approval order, an approvable letter, a not-approvable letter, or a denial by that date, absent a major amendment or an advisory panel referral, either of which can extend it under § 814.37 and § 814.44. A 510(k) carries no equivalent obligation in the statute itself. What people call “the 510(k) clock” is FDA’s own internal performance goal, renegotiated with industry roughly every five years under MDUFA and published in that cycle’s performance goals and procedures letter. FDA aims to meet that goal on the large majority of submissions, but missing it is not a violation of anything — it is a missed internal target that gets reported back to Congress, not a missed legal deadline the way a lapsed PMA period would be.

Building a date you can defend

None of this is an argument for refusing to give a date — stakeholders need one, and declining to estimate reads as evasiveness rather than rigor. It is an argument for building the estimate around the right unit. Quote FDA’s active review days as what they are: a goal for FDA’s own clock, not a prediction of your calendar. Then add your own team’s honest estimate of how long at least one round of hold-and-respond will take, because a well-prepared response to an Additional Information request still takes real days to draft, route for internal sign-off, and submit — and that time sits entirely on your side of the ledger, not FDA’s. A submission readiness review done honestly before filing is the best lever you have for keeping that round count to one, since most holds trace back to a gap the team already half-suspected going in. When you present the estimate, separate the two clocks explicitly — FDA’s goal is X active days; your own realistic total, including at least one response cycle, is Y calendar weeks — so that if FDA’s side runs long, nobody mistakes it for your team being behind.

Where this goes wrong

Quoting the MDUFA goal as a guarantee

FDA’s performance goals describe what the agency aims to hit on most submissions across a user-fee cycle, not a deadline it owes any individual sponsor. Presenting the goal days as a promised date sets up a conversation you will regret the first time a submission needs a second round of questions.

Charging your own response time to FDA’s clock

The days between an Additional Information or deficiency letter and your complete response are not days FDA is reviewing anything. If a stakeholder asks why a submission is taking longer than the quoted goal, check whose clock the elapsed time actually belongs to before assuming FDA is behind.

Treating a 510(k) and a PMA as the same kind of commitment

A PMA’s 180 days comes from the statute itself, under 21 CFR § 814.40; a 510(k)’s 90 days comes from a negotiated goal that gets renegotiated every MDUFA cycle. Confusing a statutory period with a performance target misstates how much certainty either one actually gives you.

Reading the clock correctly also means reading what it does not promise: neither figure says anything about substantive outcome, only about timing. For the mechanics of how a 510(k) actually moves from submission through a hold and back out the other side, the review walkthrough in the 510(k) course is worth a careful read before you quote a date to anyone above you.

Sources & further reading

eCFR — 21 CFR § 814.40, Contents and period for review of a PMA ecfr.gov
eCFR — 21 CFR § 814.44, Procedures for review of a PMA (major-amendment extension) ecfr.gov
FDA — MDUFA Performance Goals and Procedures, current reauthorization letter fda.gov
Regulatory Academy — The 510(k) Review: From Submission to the SE Letter regulatoryacademy.com
Regulatory Academy — Responding to an FDA Additional Information Request regulatoryacademy.com
Regulatory Academy — How to Run a Submission Readiness Review regulatoryacademy.com

This essay is provided for general educational purposes and reflects the regulatory landscape as of its publication date. It is not legal, regulatory, or career advice.