I started a business in 2024 but just used my personal vehicles for business 30% of the time. What do I put for vehicle basis?

[nhillmer49]

schedule c what is investment at risk box mean?

[VolvoGirl]

Schedule C line 32  - at Risk Investment.   If you don't know what it means then probably All your Investment is at Risk (check Box 32a). It means you are using your own money for the business.  So you need to check 32a  all investment is at risk.    If you have money not at risk you can not take a loss on schedule C.

And some expenses, such as home office or section 179 depreciation can only be used to reduce your schedule C taxable income to zero, and not to create a loss. Excess deductions for these carry over to the next year. And you have to answer yes to both questions about exclusive and regular use, not just one. The area of your home office must be used regularly and exclusively for business to deduct it.

[Mike9241]

for vehicle cost it's the lower of your actual cost or fair value when placed into service.  you only need this if you take depreciation. you can instead use the standard mileage deduction.