I worked in London for all of 2006, January thru December, and made £28K and paid £2375 EES NI and £3050 ERS NI and £5049 in tax. I'm back in the States about to begin work again. Do I file in the US for my UK income and will I have to pay? I appreciate any help offered.
You need to file in the US but likely will not have to pay as it is under the income exclusion allowance.
More importantly, you need to file in the UK. From what you said, it appears you have overpaid your UK taxes. If I simplistically assume you made £7,000 in the first 3 months and £21,000 in the second nine months (£28,000 total) than your taxes should be:
2005-2006 UK Tax Year
£4,895 untaxed (personal allowance)
£2,090 at 10% tax rate
£15 at 22% tax rate
Therefore tax is £212 (.10*2090+.22*15)
2006-2007 UK Tax Year
£5,035 untaxed (personal allowance)
£2,150 at 10% tax rate
£13,815 at 22% tax rate
Therefore tax is £3254 (.10*2150+.22*13,815)
So your total inland revenue tax should be £3,467; they owe you £1,582.
It also looks like you've been overtaxed on NI but I haven't done that calc.
Again, this is a simplified look at it so my numbers wont be 100% accurate, but I'd say they very likely owe you £££. You'd have to consider other UK income such as interest earned in bank accounts, etc.