True. But the value of writing that may not have to be whether or not it is legally binding. It could just serve the purpose of being a little nudge for the recipient to get off their keister and cash or deposit it.
I'd say that even with the amount of time that's passed, you still need to continue trying to contact this person. At least establish that he's not replying. How are you corresponding? Email, phone calls? I'd go the registered mail route myself. With proofs of reciept.
