Form 14653, Certification by US Person Residing Outside of the US, to certify that your prior lack of filing was non-willful (Form 4643 under the domestic version of the procedure)
Form 1040, US Individual Income Tax Return, for each of the three most recent years. In the case of a non-resident alien, Form 1040NR can be filed.
FinCEN Form 114, Report of Foreign Bank and Financial Accounts (FBAR), for the last six years
If applicable,
Form 2555, Foreign Earned Income Exclusion
Form 1116, Foreign Tax Credit
Form 8938, Statement of Specified Foreign Accounts