It's common for someone who moved between the US and India to discover, years later, that they should have been filing FBAR (FinCEN Form 114) or Form 8938 for Indian bank accounts, PPF, or other holdings, and simply didn't know. For taxpayers who were genuinely non-willful about it -- and who are not already under IRS audit or examination -- the Streamlined Filing Compliance Procedures exist to bring them into compliance with most penalties waived.
What 'streamlined' actually requires
There are two tracks: the Streamlined Domestic Offshore Procedures for taxpayers who were US residents during the relevant years, and the Streamlined Foreign Offshore Procedures for those who met the non-residency requirements. Under either, the general rule is filing the three most recent delinquent tax years' returns (regardless of how many years were actually missed) and the six most recent delinquent FBAR years, along with a signed certification of non-willfulness.
The IRS discontinued the separate Delinquent FBAR Submission Procedures as a standalone public option; for most people who are behind on FBAR specifically, Streamlined is now the relevant compliance path if they qualify, rather than a simpler standalone FBAR-only fix.
FBAR and FATCA are not the same filing
A frequent point of confusion: FBAR (filed with FinCEN, not the IRS, above a $10,000 aggregate foreign-account threshold) and Form 8938 under FATCA (filed with the tax return, with its own separate and generally higher thresholds) are two different requirements under two different legal authorities. Filing one does not satisfy the other, and someone catching up may need to address both. Given the certification of non-willfulness carries real legal weight, this is a case where working with a preparer experienced in cross-border compliance is worth the cost.