If you are deducting mileage for the car then the car insurance is not deductible. The mileage deduction includes things like wear and tear and oil changes and insurance.
If you are not deducting mileage and are instead using actual auto expenses then the insurance is deductible for the percentage of business use. So you multiply the business use percentage of the car times the amount that you paid for the insurance and that will get you to your deduction.
If the car is used 50% for business then you will deduct 50% of the insurance, etc.
@silbert
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