Go to this IRS website for using Direct Pay - https://www.irs.gov/payments/direct-pay
After entering the type of payment you will be making the IRS website will require this -
Direct Pay verifies your identity using information from your 1040 filing history. Please provide the following information from a 1040 tax return you filed during the previous six years.
Note: the Tax Year for Verification you enter here does not have to match the tax year for your payment.
