IRS Business Codes
Business codes are used by the IRS to categorize your business for statistical purposes only. Whatever code you enter will not affect the outcome of your income tax return.
TurboTax helps you find your business code. When going through the screens for your business, you'll see a screen that has a Lookup Business Codes button. Just click on the button and enter the keywords for your business. Click Search and choose the right code. If none of the codes apply, it's ok to enter 999999 however you won't be able to file your tax return electronically. You'll have to mail it.