It is still a contract. You lent him money and he agreed to pay it. Sue for breach of contract. You can get court fees and interest on your claim. You have to prove you lent him money and he agreed to repay it.
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You choose "contract" and add court fees to the amount you are seeking. The suit must be filed in the county of residence of the person you loaned money to. You don't need a written contract to file suit, but keep in mind that this person may testify that there was no loan made and the judge will be faced with determining the credibility of each person to determine if a loan was made. For that reason you should bring any and all evidence that shows, or tends to show, that you did loan money.