The above is interesting but doesn't give enough insight, to figure out how to do a quarterly estimate, outside of when I electronically file the tax return. Here it is 12/31/2020 and I have a client whos return was timely filed on 4/15 but I've determined, from 2020 results that a 4th quarter estimated tax deposit should be made for both Federal and California.

I gather, from what you are indicating that for Federal, I cannot do it through Proseries but for California, I can. I don't understand how I can establish an electronic filing now for a locater that was previously filed so that I can file a quarterly estimate.

And, yes, in the past, although I'm uncomfortable using the taxpayer's information this way, I've gone on to the tax jurisdictions site and made quarterly estimates.