Start with FDA Guidance, "Deciding when to submit a 510(k) for a change to an existing device" and follow it closely. In your letter to file, provide detail of your changes, and document a strong justification and your best argument for why your justification is adequate. Do not just create a checklist from the guidance and check the boxes that apply. It's much harder to defend your decision in an audit if the letter to file contains only checked boxes rather than details of why the decision was made. And include engineering level detail in the justification. Also remember that the letter to file should be based upon cumulative changes since the submission. Be very cautious of cumulative changes, and as regulatory, take a stance when it's time to submit.
GLOBAL BOTTOM CTA INSTRUCTIONS:
To display custom copy instead of global copy in this section, please go to Show Global Content for Bottom CTA? toggle in the "Contents" tab to the left, toggle it off, save, and then REFRESH the page editor, the custom text will then show up and ready to be edited.
Turning the global content back on will be the same process, go to the toggle and toggle it back on, save and refresh!