You can make estimated tax payments to the IRS at www.irs.gov/payments. Also, I can't stress this enough. After you make each quarterly tax payment *PRINT* *YOUR* *RECEIPT* and file it with your 2021 tax information so you'll have it next year when you go to prepare and file your 2021 tax return.
If your state also taxes personal income, you'll need to make estimated payments to your state taxing authority too. How you would make those payments depends on your state, as not all states offer the ability to pay estimates on line. You'll need to check your state's dept. of taxation website for that.
