British Expats - E-verify advice

This is the reply I got back.

One thing that comes to mind is you don't have to prove it when you apply for benefits. To receive benefits in the U.S. you have to be a U.S. citizen or legal alien. So when it comes time to apply you are going to need to prove it, since your SSN record still has you listed as an alien. If it shows you as a U,S, citizen you don't need to prove it again, but an alien would have to prove they are legally in the country

With that you kind of get a 2 fer. U.S. citizens age 60 or older applying for benefits don't need to prove their age if the date of birth given isn't materially different than the date of birth on the SSN record.

Getting benefits outside the U.S. is going to depend on your country of citizenship and residence, but U.S.and U.K. citizens are pretty much equal when it comes to receiving benefits outside the U.S.

You could get hit with the alien tax withhold, but it isn't going affect a U.K. citizen receiving benefits outside of the U.S.

That's all I'm aware of, but I'm sure there are things that use SSA citizenship info to establish eligibility.