Short answer. Article 1378 resolves this exact deadlock: once every other interpretation rule genuinely fails, and your contract is onerous, like a sale or lease, the doubt shall be settled in favor of the greatest reciprocity of interests. The reading that keeps the exchange most balanced between you and the other party controls.
What the law says
If the contract is onerous, the doubt shall be settled in favor of the greatest reciprocity of interests.
Civil Code, Article 1378 — Doubts of Last Resort. Read the full provision →
This principle only applies once other rules are exhausted
Article 1378 opens by making clear this is a rule of last resort: it applies "when it is absolutely impossible to settle doubts by the rules established in the preceding articles." A sale or a lease is not automatically thrown into this provision the moment a clause is unclear. The other established interpretation rules have to be tried and found genuinely unable to resolve the ambiguity first. Only once that threshold is met does the specific rule for onerous contracts take over.
The rule for your sale or lease: greatest reciprocity
Because a sale or a lease is an onerous contract, both sides give something in exchange for what they receive, Article 1378 supplies this guiding principle: if the contract is onerous, the doubt shall be settled in favor of the greatest reciprocity of interests. Between the competing readings you and the other party are offering, the one that preserves the most balanced exchange of value, rather than favoring one side at the other's expense, is the interpretation the law prefers.
Why onerous contracts get a different tilt than gifts
This rule stands in deliberate contrast to how the article treats a gratuitous contract like a donation, where doubt is resolved in favor of the least transmission of rights, protecting a party who is giving something for nothing. A sale or lease is different: both sides bargained for something and gave something up to get it. Resolving ambiguity in favor of the greatest reciprocity respects that both parties came to the table expecting a fair exchange, rather than assuming one side intended to give more than it received.
The outer limit: doubt over the principal object
This principle is not unlimited. Article 1378 draws a firm line for doubts that go deeper than incidental terms: "if the doubts are cast upon the principal object of the contract in such a way that it cannot be known what may have been the intention or will of the parties, the contract shall be null and void." So if the disagreement between you and the other party is not about a peripheral clause but about the very core of what was being sold or leased, and that core intention genuinely cannot be determined, the contract itself fails rather than being rescued by this interpretive rule.
Cases citing this provision
These Supreme Court decisions cite the provision above. We list them so you can read them yourself; the summaries of what each decided are not ours to give.
- Merlinda Plana vs. Lourdes Tan Chiua and Heirs of Ramon Chiang, G.R. No. 250636, January 10, 2023 — read the decision on LawPhil →
- Heirs of Mary Lane R. Kim, represented by Kim Sung II, Janice Kim, G.R. No. 249247, March 15, 2021 — read the decision on LawPhil →
- Spouses Rene Luis Godinez and Shemayne Godinez vs. Spouses Andrew T. Norman and Janet, G.R. No. 225449, February 26, 2020 — read the decision on LawPhil →
- United Planters Sugar Milling Co., Inc. (UPSUMCO) vs. The Honorable Court of Appeals, et al, G.R. No. 126890, April 2, 2009 — read the decision on LawPhil →