or you can skip the mailing completely by using the IRS payment website. then there is no need to print or mail the 1040-es. with Direct Pay you enter the year (2020) and select estimated tax payment. the USPS has been tardy in processing some mail. if they process as 1/16/2021 you're a day late. with Direct Pay you specify the amount and date it is to be taken which should be 1/15. you get to print a receipt as proof.
https://www.irs.gov/payments
