Assuming you're asking about deducting car expenses on your personal taxes in the United States:
There are a few different ways that you can deduct car expenses on your taxes. The most common way is to deduct them as part of your itemized deductions. You can also deduct certain car expenses if you use your car for business purposes.
If you itemize your deductions, you can deduct your actual car expenses, or you can take a standard mileage deduction. The standard mileage deduction is a set amount per mile that you can deduct for using your car for business, charitable, medical, or moving purposes. For 2020, the standard mileage deduction is 57.5 cents per mile.
To deduct actual car expenses, you'll need to keep track of all the money you spend on things like gas, oil changes, repairs, and insurance. You can also include the depreciation expense of your vehicle over time.
If you use your car for business purposes, you can deduct all of your actual business-related expenses. This includes things like gas, repairs, and insurance. You can also depreciate the value of your vehicle over time if it's used primarily for business purposes