I end up writing off about £100 a year due to bad payers. All small amounts £8-£12. Some it's unavoidable, death and serious illness. There's always a few who are just bad customers, either got terrible memories or just don't see us seriously enough to be bothered. But like others have said, you get a nose for who they are and drop them. I seldom forget a bad customer, even after years and if they ever ask me again, I ask for what they owe first before l even consider a restart. However, it hardly ever happens because they still don't pay up even when they promise to.