JAJ

Selective Service can be found at http://www.sss.gov
Assuming you are male, you have to register. If you don't, you are breaking the law and it may cause problems for you later on.

They will accept a late registration as long as you have not turned 26. Most people in your situation only come and ask when they are 26 or 27 and it's too late.

If you have a British registration certificate then you should read what it says for the section of the British Nationality Act 1981 under which you were granted British citizenship. If it says section 1(3) then you are British otherwise than by descent. Or perhaps it says something else?

On taxes, you may not have any tax to pay for now but you should file U.S. federal tax returns anyway to make sure the IRS knows your liability is zero. And going forward, you will need to keep your investments quite simple in order to avoid complexities with American taxes. Owning stock and real estate directly doesn't usually cause complications but it's generally advisable to avoid mutual funds (unit trusts) for example and you don't really get to make use of U.K. tax free savings like ISAs because they are not tax free to the United States.

nun

Definitely avoid UK stocks and shares ISAs, They are taxed by the IRS as foreign grantor trusts and will probably own Passive Foreign Investment Corporations (PFIC) ie unit trusts which you should avoid. But a cash ISA is a good investment. It grows UK tax free, but you will have to declare any interest on your US taxes.....however you might well have no US tax to pay if you have enough UK tax credits.

Banu_Hashim

Yes, I do.