I earned minimal (very little) employment income; am I required to file an annual federal and state tax return?
Yes, the Federal government requires any NRA who generates United States source income to file a United States tax return, regardless of the amount of income or tax liability. For the California government, generally, if your annual gross income is less than $11,000, you are not required to file, unless you have paid some state income taxes in advance and want to request a refund.