It depends on a couple things:
If your business expenses are "job related expenses" meaning they are unreimbursed from your W-2 employer, those expenses are not deductible in 2018. The Tax Cuts and Jobs Act of 2017 suspended the miscellaneous deductions that were subject to the 2% floor on the federal return for the years 2018 to 2025. Some states still allow the deduction for job-related expenses, therefore they can still be entered into the federal return and TurboTax will determine if they can be deducted on the state return.
If your business expenses are for a self-employed business, then those are deductible whether you itemize or take the standard deduction on your return. See the FAQ for entering self-employed business expenses on Schedule C in your return.
https://ttlc.intuit.com/replies/5802554
