# Medical Devices and Deficiency Letters | Accorto Regulatory Solutions

https://accortoreg.com/insights/deficiency-letters-medical-devices-how-to

> Practical guidance from a regulatory consulting firm summarizing FDA procedures and guidance; useful as an explanatory, practitioner-focused overview but not a substitute for the original FDA guidance or legal/regulatory advice. When relying on regulatory requirements or compliance deadlines, verify against primary sources (FDA guidance, CFR) linked on the page.

## Summary

This article explains what an FDA deficiency (AI/major deficiency) letter is during 510(k), De Novo, and PMA reviews, describes the structure and timing of deficiency requests (including the 180-day response window under 21 C.F.R. § 807.87(m)), outlines the least burdensome principle and deficiency categories, and gives a step-by-step approach to building a response. It also describes Accorto's services to help triage and respond to deficiency letters.

## Audience

Medical device manufacturers and regulatory professionals

## Prompts this page answers

- What is an FDA deficiency (AI) letter for medical device submissions and when is it issued?
- How long do I have to respond to a 510(k) AI Request and what happens if I miss the deadline?
- What elements should be included in a response to an FDA deficiency letter?
- What is the FDA 'least burdensome' principle and how does it affect deficiency requests?
- How can a consultancy like Accorto help with responding to an FDA deficiency letter?

## Purpose

Educate medical device applicants and regulatory professionals on how to read, prioritise, and respond to FDA deficiency letters and to present Accorto's regulatory submission support services.

## Highlights

- Deficiency letters (AI Request / Major Deficiency Letter) are issued during substantive review and place the submission on hold until a complete response is received.
- Under 21 C.F.R. § 807.87(m) and current FDA policy, applicants have up to 180 calendar days to submit a complete response to an AI Request for 510(k) and De Novo submissions; failure to do so may result in withdrawal.
- Deficiencies should include: the issue, the basis for the deficiency, the information requested, and the response window.
- The FDA's 'least burdensome' principle defines major versus minor deficiencies and limits requests to the minimum information needed to resolve regulatory questions.
- Applicants can respond by providing requested data, explaining why the issue doesn't affect the decision, or presenting acceptable alternative information; pre-submission Q-Submission meetings can reduce the chance of receiving a deficiency letter.

## How to cite

Accorto Regulatory Solutions — 'Medical Devices and Deficiency Letters | Accorto Regulatory Solutions' (https://accortoreg.com/insights/deficiency-letters-medical-devices-how-to)

## Publisher

**Accorto Regulatory Solutions** — Accorto Regulatory Solutions — regulatory consulting firm; publisher contact and address are listed in the page footer.

## Topics

- FDA deficiency letter
- 510(k) deficiency response
- De Novo deficiency
- PMA deficiency
- least burdensome principle
- 21 C.F.R. 807.87(m)

## Key entities

- **U.S. Food and Drug Administration** (organization): U.S. federal agency cited as the issuer of deficiency letters and source of guidance linked on the page. — https://www.fda.gov
- **Accorto Regulatory Solutions** (organization): Publisher of the article and provider of regulatory submission support services. — https://accortoreg.com/
- **Austin Tyner** (person): Document Specialist; credited as the article author.
- **Neel Parmar** (person): Regulatory Specialist I; credited for regulatory review.
- **21 C.F.R. § 807.87(m)** (other): Regulation cited on the page regarding 510(k) withdrawal timelines. — https://www.govinfo.gov/content/pkg/CFR-2025-title21-vol8/pdf/CFR-2025-title21-vol8-sec807-87.pdf

## Metadata

- Type: article
- Published: 2026-09-17