This hasn't been an issue for me in years, and it's because of how I structured payments from the start — every client either prepays or has a card on file that gets charged after each visit. No invoice chasing, no awkward follow-up calls.
I'm in lawn care, so I chose the industry partly because the model works cleanly this way. Service is done, card gets charged, done. Occasionally a card expires or gets cancelled — I send a notice and it gets resolved quickly. But the exposure on any single treatment is small enough that it's never a real problem.
If you're in a trade where larger project balances are normal, I get that this is harder to enforce. But if there's any way to move toward deposits or card-on-file, it eliminates the problem entirely rather than managing it after the fact.
