What is the standard mileage deduction for the use of a vehicle in a business?

The rate varies by year and sometimes changes within a year. The rate or rates are available in various IRS documents. You can find them in IRS Publications 17 and 334. Rates for prior years be found on the IRS Standard Mileage Rates page. Note that the rate for business travel was increased by 4¢ to 62.5¢ effective July 1, 2022.