If you are a US citizen, you have to submit a tax return every year, no exemptions. If you are PAYE, it is likely that you won't have to pay any back taxes to the IRS but you have to hold your hands up to the IRS and submit tax returns for the last 6 years.
Richard Dunn of http://taxamerican.com/ did the 6 years of returns for a client of mine recently and charged a very reasonable price. The tax attorney she had approached in the US was charging extortionate prices.