P.R. Laws tit. 10, § 1656
Debtors who delay the payment of their debts after the same have fallen due, must pay, from the day following that on which it became due, the interest agreed upon in such case, or in the absence of such agreement, the legal interest.
If the loan is in kind, in order to compute the interest, its value shall be graduated by the prices of the merchandise loaned in the locality in which the return is to be made, on the day following that on which it falls due, or by the value fixed by experts if the merchandise should no longer exist at the time its appraisement is to be made.
And if the loan consists of bonds or securities, the interest, by reason of delay in repayment, shall be that earned by such securities or bonds, or in the absence thereof, the legal rate of interest, the value of the securities being determined by their price on exchange, if they are subject to quotation, or at their current prices on the day following that on which they fall due.
History —Commerce Code, 1932, § 234.