I performed professional tax services for an individual. I had a signed contract and performed all prescribed services up to the point that I terminated the client for cause(s) (one was that he bounced a check for payment of services, which alone was sufficient grounds). I'll mention that the contract has a clause that he will pay all legal and collection costs associated with the non payment of fees. So, I fired client for breach of contract. He then paid me after I threatened to sue. Subsequent to my firing him, he has caused all kinds of trouble, leaving obscene phone messages, writing me dirty & threatening emails, reporting and making false claims to the BBB, making the same false claims to the Board governing my profession, and other. I have spent above 30+ hours undoing the problems he created and continues to create. Can I bill him for my time, or sue him for other causes (e.g., business Interference, falsification of public representations, or whatever). He shows no signs of letting up. I want to shut him down. Clearly, he's retaliating for my firing him and not completing the work. I'm thinking that even though I've fired him, all my time spent re: this previous client is still ongoing and related to the "collection" matter, as it all about seeking a refund by him. Or is it a stretch to sue him on those grounds? Please advise.