In the past , my “real ES” became much greater than the original ES calculated when the 1040 was originally calculated. This was due to an unanticipated windfall. We merely calculated the difference and sent in the increase in the ES at the appropriate remaining payment times (June 15, September 15, January 15). That’s all. When the subsequent 1040 was calculated the next year the appropriate real total ES contribution was annotated which had included the increased payments. All went OK and the tax and payments went through without a hitch. So, yes, you can use IRS. gov to pay your “new” ES BUT be sure to do two things: 1) check the e-mail confirmation of payment to be sent to you and 2) identify the payment(s) as an estimated tax payment(s).
