When you get the gains or dividends or sell you can send in an extra estimated payment then.
Here are the blank Estimates and instructions…..
http://www.irs.gov/pub/irs-pdf/f1040es.pdf
The 1040ES quarterly estimates are due April 15, June 15, Sept 15 and Jan 18, 2022. Your state will also have their own estimate forms.
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
