I am a CPA. Previously, when I worked at a firm, there were assistants to help me manage a lot of the nitty-gritty details. Like double checking that an E-file didn't get rejected, or making sure an obscure deadline didn't get missed, they filed the extensions. It was someone else's job to do the payroll, the sales tax, the bookkeeping. I didn't even have to be organized - they just brought me the files to work on and I dropped them off somewhere when I was finished.
When I became self-employed, I suddenly was responsible for everything. All the little details that make a good accounting firm. How do I keep all of this in my head and still have room for tax law?
Checklists are invaluable. I have a monthly checklist with all of my clients listed who have monthly tasks. I have calendar reminders. I keep To-Do lists. I make a habit of reviewing all of the original emails and documentation for complicated situations before sending out my final opinion, to make sure I haven't missed anything (I usually have, thank goodness I review).
But I still routinely encounter issues - for instance, when I do payroll in multiple states, many states have different deadlines, different payment dates, different agencies, extra forms, extra rules, etc. Before I do payroll in a new state, I reminder myself not to assume I know it all. Instead, I Google it like I'm doing payroll for the first time. type in "How to file payroll California" and "payroll tax forms California."
Checklists are absolutely invaluable. When I get a new task, I make a checklist. Sometimes I don't have to revisit them after awhile, because what I'm doing is second nature. But they're especially helpful when you learn a process and then you might not encounter it again until 6 months later.
But you can't win everything. 1040s are second nature to me, and I'd gotten pretty decent with 1040-NRs. But I don't know everything. When income reaches a certain threshold, I'm supposed to attach tax treaty documentation instead of just noting which tax treaty provision I'm using (didn't find that out until a client got an IRS notice, but it was right there in the instructions), international students who are exempt from FICA are supposed to file a certain extra form (I learned that while working for TurboTax, and realized that I hadn't told a client they needed that). These are items that it turned out were easy to Google - I just didn't think to do it.
I've had to train myself to say, "You're not great with details - remember to review everything." "This is a new client situation - do some research to see what special issues face this industry." "You don't do a lot with this state, remember to look out." "You've backed into three different cars in your own driveway. Remember to check behind you when you put the car in reverse. Then double check. And check again. Seriously, stop backing into shit."