You can use the IRS tax payment website for your 2020 estimated tax payments - https://www.irs.gov/payments
Or if you are using the paper IRS Form 1040-ES for mailing you payment, then go to this IRS website for where to mail based on your state of residence - https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment
