â G.A. A. The TGIF (Thank God It’s Filed) date of May 17, 2021, also applies to state income tax returns since most reports to individual states use Adjusted Gross Income from the 1040 as the starting point for their tax computation. However, Wednesday, April 15, is still the day when an estimated tax payment for the first quarter of 2021 is due. Taxpayers who became part of the “gig” economy as a result of the pandemic are being alerted about this quarterly payment that attempts to “mirror” the withholding of taxes, which is “pay as you go” Here’s a “Cliffs Notes” version of how to tackle the task, compliments of the Form 1040ES packet available at www.irs.gov, which includes all of the elements mentioned below.