P.R. Laws tit. 31, § 5126
2019-02-20
The proof of payment is incumbent upon the person who claims to have made the same. He shall also be obliged to prove the error under which he made it, unless the defendant denies having received the thing claimed from him. In such case, if the plaintiff should have proven the delivery, he shall be released from any further proof. This does not limit the right of the defendant to justify that what he is supposed to have received was due him.
History
—Civil Code, 1930, § 1800.