P.R. Laws tit. 31, § 3178
2019-02-20 00:00:00+00
When the payment cannot be applied according to the preceding rules the debt which is most onerous for the debtor among those which may be due shall be considered as the one paid.
If the latter should have the same nature and charges the payment shall be applied to all pro rata.
History —Civil Code, 1930, § 1128.