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    Letter to File

    Internal documentation justifying that a device change does not require a new 510(k) submission.

    Reviewed by Christian Espinosa, Founder, Blue Goat CyberLast reviewed May 5, 2026

    Definition

    A Letter to File is a manufacturer-prepared rationale, retained in the device's design history, explaining why a change does not significantly affect safety or effectiveness and therefore does not trigger a new 510(k).
    What the regulation says
    The FDA guidance "Deciding When to Submit a 510(k) for a Change to an Existing Device" provides criteria for when modifications require a new 510(k) submission versus when a Letter to File (LTF) is appropriate. Similarly, ISO 13485:2016, clause 7.3.9, addresses control of design and development changes requiring documentation and verification. The EU MDR, in Annex I, emphasizes the need to manage and document changes impacting safety and performance. Regulators expect comprehensive documentation justifying the decision not to submit a new premarket notification.

    What this means in practice

    FDA's 'Deciding When to Submit a 510(k) for a Change' guidance provides flowcharts. LTFs are scrutinized during inspections; weak rationales are a common Form 483 finding.

    Examples

    • A manufacturer makes a minor change to the color of a device's casing without altering its material, function, or performance, documenting this decision with a Letter to File.
    • An update to a device's software primarily improves user interface aesthetics without affecting any clinical algorithms or safety features, justified by an LTF.
    • A supplier change for a non-critical component where the new component is shown to be functionally equivalent and poses no new risks, documented via a Letter to File.
    Common pitfalls
    • •Failing to provide objective evidence and a robust scientific rationale for the decision is a common pitfall.
    • •Inaccurately assessing the impact of a change on device safety or effectiveness can lead to regulatory non-compliance.
    • •Not obtaining necessary expert reviews or management approvals for the Letter to File can be a critical error.
    • •Treating a Letter to File as a routine administrative task rather than a critical regulatory decision is a common mistake.
    • •Neglecting to update relevant risk management files (e.g., in accordance with ISO 14971:2019) after a change is a significant oversight.

    Frequently asked questions

    A Letter to File is used when a manufacturer determines that a change to a legally marketed device does not significantly alter its safety or effectiveness and therefore does not necessitate a new 510(k) submission to the FDA.

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    Primary references

    3 sources
    Link health: 3 verified· last checked 2026-06-20
    FDA·2RAPS·1
    1. 1
      Deciding When to Submit a 510(k) for a Change
      Verified
      FDAfda.gov
    2. 2
      RAPS Regulatory Focus
      Verified
      RAPSraps.org
    3. 3
      FDA - Medical Devices
      Verified
      FDAfda.gov

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