Short answer. Because a partition of inherited property is not treated as an ordinary bargained-for exchange. If an heir received property worth more than a quarter less than their proper share, that heir can demand rescission for lesion alone, without separately proving fraud, mistake, or undue influence -- something an ordinary seller or buyer cannot do on price alone under Article 1355.
What the law says
Except in cases specified by law, lesion or inadequacy of cause shall not invalidate a contract, unless there has been fraud, mistake or undue influence.
Civil Code, Article 1355 — Lesion or Inadequacy of Cause. Read the full provision →
The general rule stays the general rule
Article 1355 still governs every ordinary sale or exchange: getting a bad price, by itself, is not grounds to undo the deal. A seller who later regrets accepting too little, or a buyer who overpaid, stays bound unless they can also show fraud, mistake, or undue influence pushed them into it.
The law accepts that people sometimes strike bad bargains honestly, and it is not the courts' job to rewrite every lopsided deal just because one side later feels shortchanged.
The exception the article itself points to
The phrase 'except in cases specified by law' is not decorative. A handful of provisions elsewhere in the Code make inadequacy of price a ground for relief on its own.
Rescission of a partition among co-heirs for lesion of more than one-fourth is the leading example: an heir shortchanged by that much can ask a court to undo the partition without proving any of the usual vices of consent.
Why partition gets special treatment
Heirs dividing an estate are not always dealing at arm's length or with equal bargaining power, and the law treats the fairness of the shares as worth protecting directly, rather than leaving heirs to the harder task of proving fraud or undue influence against a sibling or co-heir.
A partition is also not a true bargained-for exchange the way a sale is; it is meant to give each heir their fair share, so a gap of that size is treated as a red flag on its own.
What this means for an ordinary buyer or seller
Outside these named exceptions, a low price is a business risk, not a legal defect. Anyone who feels shortchanged in an ordinary sale still has to point to fraud, mistake, or undue influence, or to one of the law's own carve-outs, to have any real chance of undoing the contract.
Knowing which category a transaction falls into, an ordinary sale versus something like a partition, often decides whether a lopsided price is just bad luck or an actual legal problem.
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.
- Spouses Domingo and Lourdes Paguyo vs. Pierre Astorga, et al, G.R. No. 130982, September 16, 2005 — read the decision on LawPhil →
- Spouses Bernardo Buenaventura, et al. vs. Court of Appeals, et al, G.R. No. 126376, November 20, 2003 — read the decision on LawPhil →
- Manuel A. Torres, et al. vs. Court of Appeals, et al, G.R. No. 120138, September 5, 1997 — read the decision on LawPhil →
- Eduardo M. Cojuangco, Jr. vs. Republic of the Phillipines, G.R. No. 180705, November 27, 2012 — read the decision on LawPhil →
Related provisions
- Civil Code, Article 1355 — Lesion or Inadequacy of Cause
- Civil Code, Article 1098 — Rescission for Lesion