It may be referring to the business code in your Business profile.
Business codes are used by the IRS to categorize your business for statistical purposes only. The code you enter won't affect the outcome of your tax return.
When your set up your business in TurboTax, you'll eventually come to the Enter Your Business Code screen.
Select Lookup Business Codes, enter some keywords that describe your business (for example, day care, bookkeeping, door-to-door), and then select Search.
Select the code that most closely resembles your business's activities. If you can't find a code that applies, you can enter 999999.