In the realm of Philippine civil law, under the Civil Code, contracts are typically consensual in nature, which means that they are perfected by mere consent (Article 1315). Once the parties involved in a contract reach an agreement, the contract becomes binding, regardless of the form in which the contract is documented or the subject matter. However, there are notable exceptions to the rule of consensuality, wherein certain contracts require additional formalities or specific formalities for perfection. These exceptions can be classified into contracts that require:

Formality for Validity (Contracts Requiring a Special Form for Validity)
These contracts must comply with particular formal requirements for the contract to be considered valid. Failure to meet these formalities renders the contract void or unenforceable. The Philippine Civil Code specifies several contracts that need a particular form for validity:
- Donations of Immovable Property (Article 749): Donations of real property must be in a public instrument, and the acceptance must also be in a public document or notarized. If this formal requirement is not met, the donation becomes void.
- Sale of Large Cattle (Article 1581): Sales involving large cattle, such as carabaos, horses, or cows, must comply with the legal formalities outlined in special laws, including registration of sale.
- Antichresis (Article 2134): This contract requires that the property and the terms be in writing, as it pertains to the use of property in exchange for debt or interest payments.
Formality for Enforceability (Contracts Subject to the Statute of Frauds)
The Statute of Frauds, contained in Article 1403 of the Civil Code, states that certain agreements must be in writing to be enforceable in court, but their lack of formal writing does not invalidate them. If they are fully executed by both parties, they may be recognized. These include:
- Agreements not to be performed within a year.
- Agreements for the sale of goods worth 500 pesos or more.
- Contracts involving surety or guaranty obligations.
- Agreements concerning the sale of real property.
- Contracts for the lease of real property for longer than one year.
- Agreements on marriage settlements other than those provided for in Chapter 2 Title IV of the Family Code.
For these agreements, if no written form exists and a dispute arises, the contract cannot be enforced in court due to the Statute of Frauds.
Formality for Proof (Contracts That Must Be in Writing for Evidentiary Purposes)
Certain contracts require written documentation for evidentiary purposes to confirm the parties' terms, intentions, and agreement. If the contract is not in writing, the courts may not recognize or give weight to claims regarding the specific terms of these contracts. For example, the Civil Code emphasizes the importance of written proof in cases involving the conveyance of real property or personal property of significant value.
Real Contracts (Contracts Perfected by Delivery)
Unlike consensual contracts, real contracts require not only mutual consent but also the actual delivery of the object for their perfection. Until delivery is completed, the contract remains incomplete. Key examples include:
- Commodatum (Article 1933): This is a gratuitous loan for the use of property and becomes binding only upon delivery of the item loaned.
- Mutuum (Simple Loan): A loan of money or fungible goods becomes enforceable only when the borrower receives the funds or goods.
- Pledge: A contract of pledge, which grants security interest in movable property, is perfected only when the property is delivered to the creditor or a third party by mutual consent.

Each of these categories emphasizes an exception to the basic principle of consensuality, demonstrating that Philippine law requires more than just agreement in specific contexts, particularly where the transaction involves significant financial, legal, or personal ramifications.