What's annoying, time consuming, complex, but crucial for your business

Getting paid in full. Some people haven't paid at all. Some borrow money. Some have paid 95% but I still have to nag them for the last 13 months for that final 5%.

I would enjoy doing business if the work was just getting the job done and not worrying about the payments. I'd be very happy to outsource this to some loan collector, who'd deal with the whole process of threatening legal action, etc. But for the most part it seems like it would make things worse.

Modern businesses regularly use dozens of software systems woven together to accomplish their tasks. Which makes it difficult to even see what can/should be automated.

You really need an overarching view of the business workflows and how they interact...

Maybe a high-level directed graph of all the processes within a business would help find opportunities for simplification and automation

QA/testing. It's not particularly enjoyable at all (especially not the whole 'test in various browsers on various operating systems part), but if it isn't done... well things have the potential to go very, very wrong indeed.

Programming