Jun 9, 2021 With the primary income tax deadline delayed until mid-May, there was only a one-month gap between that date and the June 15 deadline for quarterly estimated income tax. I couldn’t sleep Sunday, and in the accompanying wee-hours mental reckoning I came upon one of the reasons. Say it ain't so, Joe … Yep, Tuesday, June 15, quarterly estimated tax payments are due. (And though I'm retired from the road, I still have to make them given the self-employed nature of my business.) Every few weeks it seems I have some type of conversation with an owner-operator less than confident about what to do about taxes.