Under Philippine law, providing support to one's children is not merely a moral obligation but a mandatory legal duty. The Family Code of the Philippines governs the rules regarding support, ensuring that children receive the necessary resources for their growth and well-being regardless of the parents' marital status.

1. Legal Basis and Definition of Support

According to Article 194 of the Family Code, support (also known as sustento) comprises everything indispensable for:

Sustenance (Food)
Dwelling (Shelter)
Clothing
Medical Attendance
Education (including schooling and training for some profession, trade, or vocation, even beyond the age of majority)
Transportation

Who is Obliged to Give Support?

Parents are mutually obliged to support their legitimate and illegitimate children. This obligation is reciprocal; however, in the context of child support, the focus remains on the parents' liability toward their offspring.

2. Determining the Amount of Support

The Philippines does not use a fixed "percentage" or a standardized "calculator" for child support. Instead, it follows the Rule of Proportionality under Article 201 of the Family Code:

The amount of support shall be in proportion to the resources or means of the giver and the necessities of the recipient.

Key Factors Considered:

The child’s actual needs (tuition fees, milk, medical bills).
The financial capacity of the parent (salary, properties, other sources of income).
The standard of living of the family.

Note: Child support is never final. The amount may be increased or decreased by the court at any time depending on the changing needs of the child or the changing financial status of the parent.

3. The Process of Filing for Support

Step 1: Formal Demand

Before heading to court, the claiming party (usually the custodial parent) should send a formal demand letter to the non-custodial parent. This letter requests the specific amount needed for the child. Legal obligation to pay support begins from the moment it is judicially or extrajudicially demanded.

Step 2: Barangay Conciliation

If both parties reside in the same city or municipality, the case must generally go through the Lupong Tagapamayapa (Barangay) for conciliation.

If an agreement is reached, a Compromise Agreement is signed.
If no agreement is reached, the Barangay Captain issues a Certificate to File Action, allowing the party to take the matter to court.

Step 3: Filing the Petition in Court

If mediation fails, a Petition for Support must be filed in the Regional Trial Court (Family Court) where the minor or the plaintiff resides.

Requirements usually include:

Birth Certificate of the child (to prove filiation).
Evidence of the parent's income (if available).
A summary of the child's monthly expenses.

4. Support "Pendente Lite"

Legal proceedings can take time. To ensure the child does not suffer during the trial, the petitioner can pray for Support Pendente Lite (support during the pendency of the case). The court can issue a provisional order requiring the parent to start paying support while the main case is being heard.

5. Special Case: Illegitimate Children

For illegitimate children to claim support, their filiation (proof that the man is indeed the father) must be established. This is done through:

The Record of Birth appearing in the Civil Register (signed by the father).
An Admission of Paternity in a public document or a private handwritten instrument signed by the father.
In the absence of these, a court action for Compulsory Recognition (which can be filed simultaneously with the petition for support). DNA testing may be ordered if paternity is denied.

6. Enforcement and Non-Compliance

If a parent refuses to pay despite a court order, several legal remedies exist:

Execution of Judgment: The court can order the sheriff to garnish the parent's bank accounts or attach their properties.
Contempt of Court: A parent who willfully defies a court order for support can be cited for indirect contempt, which may result in fine or imprisonment.
R.A. 9262 (VAWC): Under the Anti-Violence Against Women and Their Children Act, the "deprivation of financial support" is considered a form of Economic Abuse. This is a criminal offense that can lead to a protection order and imprisonment.
R.A. 7610: Neglecting a child’s basic needs can also be considered a form of child abuse.

7. Crucial Reminders

Support Cannot be Waived: The right to receive support cannot be renounced or transmitted to a third person. Any agreement where a parent "waives" the child's right to support in exchange for something else is generally void.
Retroactivity: Support is only due from the date of the extrajudicial or judicial demand.
Representation: While one can initiate the process, it is highly advisable to seek the assistance of a lawyer or the Public Attorney’s Office (PAO) to ensure the petition is technically sound.