Examples of natural obligations

The above provision is called "prescribed civil obligation." The voluntary performance or payment by the obligor despite prescription thereof converts it to a natural obligation. However, four requisites must be present, to wit: [1] a civil obligation; [2] the right of action over such civil obligation having lapsed; [3] the lapse being due to extinctive prescriptive; and [4] performance or payment done voluntarily. The effect of this is that the obligor can no longer recover what he has delivered or the value of the service he rendered.
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When without the knowledge or against the will of the debtor, a third person pays a debt which the obligor is not legally bound to pay because the action thereon has prescribed, but the debtor later voluntarily reimburses the third person, the obligor cannot recover what he has paid. (Article 1425)
The above provision is called "reimbursement for payment by third person for a prescribed civil obligation." This is different from Article 1424 because there is a third person who makes the payment.
For Article 1425 to apply, the following requisites must concur: [1] a debt; [2] the right of action over the debt having prescribed; [3] payment made by a third person; [4] such payment being against the will or without the knowledge of the debtor; and [5] debtor's act of reimbursing the third person for the payment made. In this case, the debtor can no longer recover what he has paid; this is a natural obligation.
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In the above provision, there is a prior annulment of the contract and good faith is not a requirement.
When a minor between eighteen and twenty-one years of age, who has entered into a contract without the consent of the parent or guardian, voluntarily pays a sum of money or delivers a fungible thing in fulfillment of the obligation, there shall be no right to recover the same from the obligee who has spent or consumed it in good faith. (Article 1427)
In Article 1427, no prior annulment of the contract is required but good faith is an element. This means that the consumption of the money or fungible things must be in good faith.
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The above provision is called "voluntary performance despite failed action." This is a natural obligation triggered by the dismissal of the action or unfavorable judgment and the subsequent performance by the defendant of the obligation attempted to be enforced through the failed court action. Again, the consequence is that the defendant who pays or performs cannot recover.
"Failed" is a general term which is not even used in the rules on civil procedure. Therefore, it covers a dismissal on technical grounds or a judgment on the merits.
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The above provision is called "payment by heir." The requisites are: [1] the decedent incurred a debt; [2] his heir voluntary pays the debt; and [3] the debt exceeds the value of the heir's share.
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The above provision is called "payment of legacy by intestate heir." The requisites are: [1] there is a will; [2] the will provides a legacy; [3] the will is declared void due to formalities; and [4] an intestate heir nevertheless pays the legacy.
Note that the law distinguishes between intrinsic validity and formal validity. If the nullity of the will is due to intrinsic defects, Article 1430 does not apply.
Note that the law distinguishes between intrinsic validity and formal validity. If the nullity of the will is due to intrinsic defects, Article 1430 does not apply.