Hello Scott
Thanks for the notice. I used to mail in my quarterly payments, but for several years have used the IRS portal for payment. It's slightly clunky, but I find that it takes a bit less time than writing a check and getting the envelope, etc. It saves the government some trouble too. Here is the link:
Payments | Internal Revenue Service
I copied this link to a document that has tax procedures in it. Tidy and easy every quarter.
Loren