Working With an FDA Reviewer During a Submission

A submission does not go into a void. Somewhere inside FDA, a reviewer opens the file, works through it against a checklist and their own judgment, and eventually writes back — with an acceptance, a rejection, or, more often the first time, a question. How a submission fares from that point turns as much on how well its questions get answered as on what the original filing said. That is a different skill from writing the submission itself, and almost nobody teaches it directly.

In brief

Before a reviewer opens the technical content at all, an administrative acceptance screen checks the submission against a completeness checklist — a different step, done by different staff, from the substantive review that follows.
FDA’s authority to ask for more is written into the regulation itself: 21 CFR 807.87(l) lets the agency request any additional information it needs to make a substantial equivalence finding.
Not every question stops the clock. Minor points are often resolved informally, while a formal deficiency request is a heavier, more consequential instrument.
The most common way a submission stalls is not a wrong answer. It is a non-answer — a long response that never quite addresses the specific question that was asked.

Before a reviewer ever reads it: the acceptance screen

Before substantive review starts, FDA screens a submission’s format and completeness against a defined checklist: is the right form used, are the required sections present, does the content match what the submission type requires. This step exists to filter out incomplete filings before they consume review time, and failing it sends a submission back to the sponsor rather than into the review queue — it does not count against the formal review clock, but it does cost real calendar time. It rewards exactly the file-building discipline covered in our free 510(k) course’s building-the-file lesson: a checklist problem, not a scientific one, and worth solving completely before submission rather than treating it as recoverable later.

What a deficiency request actually is

Once substantive review begins, not every question a reviewer has rises to the level of a formal letter. Minor points are often resolved through informal, interactive contact — a call or an email — that keeps the submission moving without stopping the clock. A formal request for additional information is a different instrument: its legal basis is 21 CFR 807.87(l), which lets FDA ask for any additional information it needs to make a substantial equivalence finding, and it turns the submission into a new review cycle once it lands. The same document types keep recurring across these requests — biocompatibility testing, software documentation, labeling comparisons, predicate rationale — because an ambiguous answer in one of these areas repeats across submissions industry-wide. A reviewer’s question is very often a version of a question they have asked before, not a personal read on your specific device. The same careful, literal reading that matters for enforcement correspondence applies here too; see the submission-to-clearance lesson for the mechanics of the review clock itself.

Answering a deficiency request well

Read the actual question before drafting anything. Write down, in one sentence, exactly what is being asked — separate from what you wish had been asked.
Answer the narrowest form of the question first, directly, before adding supporting context. Reviewers read dozens of these; make the answer findable.
If anything changed in the device, protocol, or labeling since the original filing, say so explicitly and reference it by name. An unflagged change reads as an omission, even an innocent one.
Do not relitigate a technical position you have already lost. If the reviewer has stated a requirement, meeting it moves the submission forward faster than arguing it again in the same response.

Two habits that turn a fixable question into a second round

Answering the question you wish they’d asked

It is tempting to use a deficiency response as a chance to restate the strongest parts of the original submission. A response padded with material the reviewer did not ask about buries the actual answer and reads as evasive, even when nothing is being hidden.

Treating the request as an argument rather than a checklist

A deficiency letter is closer to a punch list than a debate. Responding defensively, or spending the reply explaining why the question should not have been asked, spends a review cycle without moving the submission any closer to clearance.

Sources & further reading

21 CFR 807.87 — Content requirements for premarket notification submissions, including additional-information requests at 807.87(l) ecfr.gov
FDA — Search for FDA Guidance Documents, including the Q-Submission Program guidance governing pre-submission interactions fda.gov
Regulatory Academy — The 510(k) Pathway, a free five-lesson course 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.