This situation is actually fairly common. You should begin by contacting an experienced accountant with expertise in expat taxes. He or she will be able to determine your tax situation and guide you on how many years of tax years must be filed for, and what documentation is needed to complete the necessary reports and returns. Certain complications—such as FATCA reporting, the Affordable Care Act, and Foreign Bank Account Reporting (FBAR)—may cause confusion for many expats, but experienced tax preparers can easily manage these issues and walk you through each step of the process.
There is a possibility for penalties due to late filings, but that is dependent on your individual tax situation. It will be affected by circumstances such as employment, filing status, and local tax payments. Generally, FBAR penalties have not been imposed on expats who were unaware of having to file an FBAR. As long as you are ready to file your taxes and submit the FBAR forms for previously missed years, the IRS will likely forgive any penalties that have been incurred.