you are correct as to the due date. how did you make the payment?. if it was not postmarked by 7/15 it was late. if you did it through a 7/14 e-payment, then it was timely. perhaps the payment was not sufficient to cover 45% of 2020 tax or 50% of 2019 tax. both the first and second estimated tax payments were due 7/15/2020
