I left the US 18 months ago after my H1B expired and had some money in a 401K account. For some reason, the company I had the 401K with closed the account a year after I left and sent a check to my old address as they said the account had not been paid in to. They took 20% tax from the amount and have said that I need to reclaim this from the federal government through a tax advisor. However, I am a UK citizen and live in the UK now so when I called a US tax advisor, they said they could not help.

Should the 401K company pay me this 20% and can I claim it back? I was not in the US when the account was closed and am a UK citizen so feel I should not have to pay the 20% US tax.

Also, does anyone know if money paid into Social Security and Medicare can be claimed back under any tax treaty? I have not been able to find any information on this.

Thank you.