nothing for now. the IRS should catch that you made the payments. however, you now have to determine whether you owe or are getting a refund. a refund presents no issues but you have to pay any balance due by 4/15/2020.
to make sure the IRS has a record of your estimates
https://www.irs.gov/individuals/transcript-types-and-ways-to-order-them
you want th account transcript for 2020.
