The person I am dealing with in Far east has asked me for my business license number to make invoice. I have checked with business link here and the only thing I need is to register as self employed. Is that sufficient. Please help.

Being self employed is one thing and having a business license to import and sell goods is another, but I'm speaking about the US. I have a feeling it's true in the UK too. The first is the type of business for our federal taxes and the second is the license to sell goods for state sales tax purposes, but also for federal and state taxes. In the US we get the first ID number from the feds, or we can use our Social Security number if we are a sole proprietor with no employees. We get the business license/sales tax ID from our state.