Yes you can send in a one time estimate.
Here are the blank Estimates and instructions…..
http://www.irs.gov/pub/irs-pdf/f1040es.pdf
Or You can pay directly on the IRS website https://www.irs.gov/payments
Be sure to pick the right kind of payment and year.....2021 Estimate
The payment is just an estimate. You will still need to enter the gross amount into your tax return next year and it will increase your income so the tax may be more. Then you will get credit for the estimated payment.
