Legal Question in Civil Litigation in New York

If you start a lawsuit against the debtor, you will bear the burden of proof. You are halfway there -- he admits to borrowing the money. If his position is that he repaid the money, he will assert that this is so and must testify to when, where, and how this was done.

You don't specify how much money is at stake. And the amount would likely play a role in determining the proofs. If, for instance, the sum was, say, merely in the hundreds or a thousand dollars, it will be more believable that the debtor repaid the money in cash. If, on the other hand, the money was, say, $50,000, it will not be readily believable, and, moreover, during discovery you could request from him bank records that would show the withdrawal of an equivalent sum.

If you would like, you can be in touch with me with more details and I will be pleased to evaluate what I believe your chances of success might be.

Good luck to you.