There’s another way to pay the IRS for your estimated taxes online. It’s called Easy Estimated Taxes. The reason I know is because it’s a company I started after years of being frustrated by the existing option that you mentioned: EFTPS as well as the traditional paper voucher system (yuck!).

What’s cool about our product is that you can calculate how much you owe as well as track your payments from past quarters. Lastly, you get email reminders before the deadline so you don’t forget.

I encourage you and your users to check it out.