The EIN is federal, the rest is local.

Opening a business bank account is the usual first reason. After that: hiring and running payroll, federal tax filings, and most license and permit applications, which ask for the number as a matter of course. Payment platforms and lenders tend to want it too. Any one of those is reason enough to have the number before the week you need it in a hurry.

No. The EIN is federal and comes from the IRS. The state's role was creating the entity, which happened at the Secretary of State and produced a different set of records entirely. Where the state does have a number for you, it is a tax registration for sales or employment, opened with the state's revenue side, and it exists alongside the EIN rather than instead of it.

Yes. Founders without a US taxpayer ID apply on the same Form SS-4, submitted by fax rather than through the same-day route, and the number is issued in the ordinary course. It takes longer, which is worth knowing when a bank account or a platform onboarding is waiting on it. Nothing else about the application changes, and the resulting number is identical.

The confirmation letter the IRS sends once the EIN has been assigned. It is the document banks, payroll providers and licensing offices ask for when they want proof that the number belongs to your entity. It is issued once, and it is not something you can reprint yourself, so it belongs somewhere permanent rather than in the inbox it arrived in.

If the entity has employees or sells taxable goods, most states say yes. That registration goes by different names from state to state and is opened with the state rather than with the IRS. It is triggered by what the business does, not by the EIN itself, so a company can hold an EIN for a year and only need the state registration when it hires or starts selling.

Disagreement with the state record. The legal name written slightly differently, the wrong entity type selected, a formation date that does not match the filing. None of it stops the number being issued, which is precisely the trap. It surfaces months later, when a bank compares the confirmation letter against the certificate from the state and finds that the two do not line up.