P.R. Laws tit. 32, § 2829
When the complaint is founded on the nonpayment of the rental or price stipulated in a contract, the defendant shall not be allowed to submit any proof other than the receipt or some other document stating that the payment has been made.
The proof of both parties shall include the fundamental facts of the main question at issue.
In such cases the court may, as an exception and solely at the request of an interested party, allow the joinder of a claim for the collection of money, founded on the nonpayment of the rent or price on which the eviction claim is based, with the latter, in the same judicial proceeding for eviction, following the procedure established in the Law of Special Legal Proceedings for said special legal appeal. The joinder or joint transaction of both actions shall in no way be interpreted to be prejudicial or damaging to the guarantees and terms established in §§ 2821-2838 of this title, including those provisions regarding the eviction of the defendant.
History —Code Civil Proc., 1933, § 628, renumbered as § 627 on Sept. 27, 2007, No. 129, § 4; Aug. 7, 1998, No. 197, § 2.