FYI ... it is in the forms list when you are in the FORMS mode ... and in the Search box in the Step by Step mode ... see screenshots below ...
And if you know what you want the forms to say you can just fill them in & print directly from the IRS site ... https://www.irs.gov/pub/irs-pdf/f1040es.pdf
OR ... just pay directly online and skip the forms ... https://www.irs.gov/payments
