Short answer

No. Under Philippine law, a will is not a contract. A will is a unilateral, strictly personal, revocable, mortis causa act that takes effect only upon the testator’s death, while a contract is a bilateral or multilateral agreement that generally becomes effective and binding upon perfection (meeting of the minds) and is, as a rule, irrevocable except as allowed by law or agreement.

Legal framework and definitions

Wills (Civil Code, Succession)
- Art. 783: A will is an act whereby a person, with legal formalities, controls the disposition of his estate to take effect after death.
- Art. 784: Making a will is a strictly personal act; it cannot be delegated.
- Art. 828 (and related): A will is revocable at any time before death; the testator cannot renounce this power of revocation.
- Arts. 805–806, 810: Form requirements for notarial wills and holographic wills.
- Arts. 818–819: Joint wills and mutual wills are prohibited in the Philippines (even if valid where executed by Filipinos abroad).
- Probate (Rules of Court): No will has effect until allowed by a probate court; probate examines due execution and capacity (extrinsic validity) and, as needed, intrinsic validity.
Contracts (Civil Code, Obligations and Contracts)
- Art. 1305: A contract is a meeting of minds between two or more persons whereby one binds himself, with respect to the other, to give, to do, or not to do something.
- Art. 1318: Essentials—consent, object, cause.
- Art. 1347(2): Contracts upon future inheritance are void, except cases expressly authorized by law (pactum successorium is generally invalid).
Donations inter vivos vs. mortis causa
- Art. 728: Donations that are to take effect after the donor’s death partake of the nature of testamentary provisions and are governed by the rules on succession (i.e., they must observe will formalities).
- Arts. 749, 748: Formalities and acceptance rules for inter vivos donations (they are contracts, perfected by acceptance and generally irrevocable subject to legal grounds).

Why a will is not a contract

Nature of act
- Will: Unilateral expression of the testator’s intent; no counterpart obligation or consent required from heirs/legatees/devisees.
- Contract: Bilateral or multilateral—requires consent (meeting of minds) between parties.
Effectivity
- Will: Takes effect upon death, and only after probate. Before death, it produces no transmissive effects.
- Contract: Generally effective upon perfection (unless subject to a suspensive condition or form), without need of probate.
Revocability
- Will: Freely revocable at any time before death; the testator cannot waive this right.
- Contract: Once perfected, binding (Art. 1315) and not unilaterally revocable except as provided by law, stipulation, or where rescission/resolution applies.
Personal character
- Will: Strictly personal; cannot be executed by an agent; the designation of heirs or shares cannot be delegated.
- Contract: Can be entered into by agents; obligations may be assignable unless prohibited.
Formalities and forum control
- Will: Must strictly comply with statutory formalities (attested/notarial or holographic); probate court supervision is mandatory.
- Contract: Formalities depend on the type of contract; no probate requirement.

Key consequences and common edge cases

1) “Agreements to make (or not make) a will”

Invalid. Because a will is strictly personal and revocable, a person cannot validly bind himself by contract to execute, maintain, or refrain from revoking a will. Any stipulation renouncing the right to revoke is void.

2) Contracts on future inheritance (pactum successorium)

Generally void (Art. 1347[2]). You cannot validly sell/assign/waive rights to an estate of a living person.
Exceptions occur only if the law expressly authorizes them (rare and narrowly construed).

3) Donations mortis causa vs. donations inter vivos

A disposition effective only at death is mortis causa and must comply with will formalities; otherwise it is void.
An inter vivos donation is a contract requiring acceptance, usually irrevocable (with statutory grounds for revocation), and takes effect during the donor’s lifetime.

4) Mutual/joint wills

Expressly prohibited in the Philippines (Arts. 818–819). Even if a couple wants “reciprocal” dispositions by agreement, they cannot bind each other by contract through a joint or mutual will. Each must execute separate, independent wills, each freely revocable.

5) Testamentary freedom vs. legitimes

Testamentary freedom is limited by legitimes of compulsory heirs (e.g., legitimate children/descendants, spouse, parents/ascendants in default of descendants). A will cannot impair legitimes; otherwise, reduction or inefficacy follows.
Contracts cannot be used to circumvent legitimes (e.g., disguising a mortis causa transfer as inter vivos without genuine present transfer/acceptance).

6) Will substitutes

Certain mechanisms transfer property outside the will:

Life insurance beneficiary designations (Insurance Code): paid to the beneficiary upon insured’s death; generally non-testamentary and not subject to probate, though legitime and public policy limits still apply.
Trusts: Inter vivos trusts are contracts; testamentary trusts arise under a will and thus depend on probate.
Survivorship/joint accounts: May transfer by contractual stipulation, but effect depends on clear terms and jurisprudence; they do not overrule legitimes.

These instruments are contracts (or statutory designations), not wills; but they do not convert a will into a contract. They coexist with, and are checked against, succession and legitime rules.

Formal validity of wills (brief)

Notarial (attested) will

In writing, signed by the testator (or at his express direction) in the presence of at least three credible witnesses; witnesses sign in the presence of the testator and of each other.
Observance of attestation clause and acknowledgment before a notary is required by law.

Holographic will

Entirely written, dated, and signed by the testator’s hand. No witnesses or notary needed at execution, but probate will require proof of handwriting and signature.

No will, however perfect on paper, has effect unless admitted to probate. Probate focuses on due execution and capacity; intrinsic issues (e.g., violation of legitimes, unlawful conditions) may also be examined.

Practical comparisons

Feature	Will	Contract
Parties	Unilateral (testator alone)	Bilateral/multilateral (requires consent)
When effective	Upon death + probate	Upon perfection (or agreed time/condition)
Revocability	Freely revocable before death	Generally irrevocable unilaterally
Delegation/agency	Not allowed (strictly personal)	Allowed (agency, assignment, etc.)
Governing law	Succession (formal, intrinsic limits; probate)	Obligations & Contracts
Limits	Legitimes; prohibitions on joint/mutual wills	Public policy; object/cause; form as required

FAQs

Can I promise in a contract to leave someone property when I die? No. A promise about future inheritance is generally void. Make a valid will or a legally effective inter vivos transfer (observing legitimes).

Can two spouses sign one document leaving everything to each other? Not as a joint or mutual will—that’s prohibited. Each must execute separate wills.

Can I use a contract to avoid probate? You may use non-testamentary instruments (e.g., inter vivos trust, insurance designation) but they must be valid contracts, not disguised wills, and they cannot prejudice legitimes.

If I made a will and later signed a deed of sale for the same property, which controls? If the deed is a true inter vivos transfer, the property may leave the estate; the will cannot give what the testator no longer owns. If the “sale” is simulated to defeat legitimes or not perfected, it may be ineffective.

Bottom line

A will is not a contract under Philippine law.
It is a revocable, strictly personal, mortis causa instrument that produces effects only upon death and after probate.
Attempts to bind testamentary dispositions by contract (e.g., to make, keep, or not revoke a will; to dispose of future inheritance) are invalid, except where the Civil Code expressly allows.
Sound estate planning coordinates valid wills, inter vivos transfers, and permitted will substitutes, always respecting formalities and legitime protections.

Practical advice: Work with counsel to (1) choose the right instruments; (2) observe will formalities; (3) audit effects on legitimes; and (4) plan for probate and record-keeping (originals, witnesses, handwriting proofs).