I've NEVER mailed a return for a client unless they were elderly and physically couldn't do it themselves. I don't get that at all. I send them the return with all the envelopes they need so that they just have to review it, sign it, and bring it to the post office themselves. the fact that they mail out their clients returns for them was the first sign that they're idiots.
What do I know about SOP when it comes to who puts what in envelopes? I engaged the services of an idiot on the recommendation of another idiot. Ultimately, the fault was mine for hiring idiots which makes me Lord of the Idiots.
I used to take the view that I'll do what I do best and hire others to do what they do best. Everybody's doing what they're best at, things are getting done well, and everyone's making money. Nice theory, doesn't work. These days I'll do shit myself and if I don't know how then I'll learn. I won't get people to do things unless I have to because they want to charge as much as they can, do as little as they can, and if they fuck up they shrug their shoulders while I bear the consequences.
