The file is in. The eSTAR passed its screening, the fee cleared, and somewhere in CDRH a lead reviewer opened your substantial equivalence discussion. What happens next runs on two different clocks — FDA days, which the agency's 90-day MDUFA goal counts, and calendar days, which your launch plan lives in — and confusing them is the oldest scheduling mistake on the pathway. This lesson walks the review as the portal tracker actually shows it, through to the letter — and through what the letter obligates, because clearance is not the finish line it is mistaken for.
The clock, honestly
Part one made the doctrinal point: the 90 days is a performance goal, not a statutory clock, and silence confers nothing. Here is the operational version. FDA days count only while the file is under active review. The technical screening and acknowledgment consume the first stretch of calendar time; by day 60 of FDA time the review team owes you Substantive Interaction — either “we are proceeding interactively,” with questions arriving by email while the clock runs, or notice that an Additional Information request is coming. The AI letter stops the clock entirely. However long you take to respond — and you have up to 180 days before the submission is considered withdrawn — the goal date moves with you, because your response restarts the count where it paused.
- Submission day — the fee is paid and the eSTAR uploads; nothing counts before both.
- Acknowledgment — the file survives technical screening and receives its K number.
- FDA day 60 — Substantive Interaction: interactive review, or an AI letter and a stopped clock.
- One planned AI cycle — because most first submissions get one. Budget your own response time honestly; the 180-day maximum is a cliff, not a target.
- FDA day 90 — the MDUFA decision goal. A goal date, not a launch date.
The letter — SE, or NSE
The review ends in a letter, delivered through the portal. If the finding is substantial equivalence, that letter is the clearance: no certificate follows, no seal, nothing to frame. The device may be marketed the day the SE letter arrives, and the clearance becomes public record — the database entry, your 510(k) summary, and the Indications for Use form all post where the next sponsor's predicate search will find them. If the finding is not substantially equivalent, the device lands in Class III by operation of law: the options are an approved PMA, a De Novo request if the risk profile fits, or a return to the comparison to fix what the file could not carry.
Clearance is a beginning
The SE letter starts obligations that outlast any launch. The establishment registers and the device is listed under 21 CFR 807; the device carries a Unique Device Identifier and its record enters GUDID; labeling keeps to 21 CFR 801. Your quality system now answers to the Quality Management System Regulation — the QMSR, effective February 2, 2026, which folded ISO 13485 into 21 CFR 820 — and adverse events run through Medical Device Reporting under Part 803, with corrections and removals reported under Part 806. And the oldest obligation of all closes the course's loop: 21 CFR 807.81(a)(3) asks, of every change you will ever make, whether it could significantly affect safety or effectiveness or is a major change in intended use. The comparison you cleared is the device you must keep making — or the next 510(k) is yours to file, and the course begins again at part one.
Where the last mile goes wrong
Planning launch on day 90
Ninety FDA days plus screening, plus one AI cycle at your own response speed, is how a “90-day pathway” takes five or six calendar months — the normal case, not the unlucky one. A launch plan pinned to the MDUFA goal date has already spent the contingency the statistics say you need.
Answering the AI request in installments
The clock resumes on a complete response. Partial answers do not restart anything — they sit while the 180-day withdrawal window burns, and a response the reviewer judges incomplete can leave the file exactly where it was. Assemble everything, answer every deficiency in the order asked, and send it once.
Treating the public record as an afterthought
The 510(k) summary and Indications for Use post publicly on clearance, permanently. Competitors will mine them for predicate research; plaintiffs' counsel and journalists read them too. A summary drafted in a hurry on submission week is a public document you never edited — write it, from the start, as the version of your argument the world gets to keep.
Frequently asked questions
What is Substantive Interaction?
FDA's day-60 commitment under MDUFA: by then the review team tells you either that the review is proceeding interactively — questions handled by email while the clock runs — or that an Additional Information request is coming, which stops the clock. It is the first real signal of how the file is landing, and an interactive-review message at day 60 is the best news a tracker can show.
Can I talk to my reviewer during the review?
Yes — within limits. Interactive review exists precisely so small deficiencies can be resolved by email without stopping the clock, and the lead reviewer's contact is in the acknowledgment. What you cannot do is negotiate the substance of substantial equivalence by phone, or use contact to pressure the goal date. Answer what is asked, completely and in writing, and save persuasion for the file.
What happens if day 90 passes with no decision?
Nothing automatic — no default clearance, no penalty clock. The MDUFA goal is a performance commitment FDA reports against, not a statutory deadline, and a miss obligates nothing about your device. Most decisions do arrive around the goal; when one drifts, the productive move is a status inquiry through the lead reviewer, not a launch plan that assumed the goal was a promise.
Sources & further reading
- FDA Guidance — FDA and Industry Actions on Premarket Notification (510(k)) Submissions: Effect on the FDA Review Clock fda.gov
- FDA — Premarket Notification 510(k): review process and MDUFA performance goals fda.gov
- FDA — Quality Management System Regulation (QMSR) final rule, effective February 2, 2026 fda.gov
- 21 CFR Part 807 — Establishment Registration and Device Listing; Premarket Notification ecfr.gov
This lesson is provided for general educational purposes and reflects the regulatory landscape as of its publication date. It is not legal or regulatory advice.
