My answer to How long does it take to register a business in the US?
Answer by Ken Larson:
Most most of my small business clients register their businesses themselves with the State in which they are forming the enterprise and then they register with the IRS on line. The cost is generally in the area of $75 to $200, except for California which is outlandish.
They register my going the the Secretary of State Web site for their State and downloading the appropriate form for the type of business they are forming (sole proprietorship, LLC, partnership, etc.). The complete the form, attach the payment and mail it to the address designated on the form.
Most receive their registration from the state and their identification numbers within 3 weeks. They then go on line and register with the IRS. That registration is virtually instantaneous if completed correctly.
You can download instructions for your state free of charge at “References” file in the BOX at the right margin of the site I maintain as an extension of my volunteer work: