For last hundred years I've provided envelopes for tax payments (final balance,  estimates, etc.).  A few years ago I added in a sheet I created listing Federal and all states tax payment websites and advised clients I recommend to pay online.  But I still include envelopes.

Thinking about next year - as more and more people are paying online - what are you going to do - envelopes, envelopes and list, mailing labels and list, or just online payment lists?

Note, I do have to check annually website lists for all states to make sure they are the current ones.