@EREIGER
You can simply fill in a form from the IRS to mail in just the first and only estimated payment you need since the home sold in January and was due last Monday if you did not use the estimated payment section in the program when you completed the original return... https://www.irs.gov/forms-pubs/about-form-1040-es
Or make a payment online directly : https://www.irs.gov/payments
And don't forget your state if needed.
