I'm a Green Card holder and want to apply for US citizenship, but I've had a gap in employment. What should I do?

Consult with an immigration attorney to determine the impact on your application.

Gather documentation of your employment history and gap.

You can simply list your employment dates, and any gaps will be assumed as periods of unemployment, which isn't an issue for US citizenship applications; consider mentioning "unemployed" if you feel it necessary for clarity