The Federal Tax Identification Number is also known as the Employer Identification Number (EIN). It is a nine digit number assigned by the Internal Revenue Service (IRS) to identify tax accounts of employers and certain others who have no employees. had to file a Form SS-4 but the entire process can now be done free online by going to the IRS website. After typing in (keyword "EIN") you will find the EIN application in an interview style format. sole proprietors to know that you may only have one EIN, no matter how many different businesses you operate.

Those that have been assigned an EIN as a Household Employer must also use that number for their sole proprietor needs as well. , non-profit associations, trusts, estates of decedents, government agencies, certain individuals, and other business entities all use EINs. 

It was very common for a provider to have begun their practice years ago and to have started out billing under their social security number. Many did this because it was just easier. their practice was bigger. The problem is that switching from a social security number to an EIN number is not a simple task and it usually freaks your accountant out. Actually, the problem is that the accountant doesn't understand that it is a problem with the insurance carriers and they switch them over without advising them.