In the Philippines, the right of a child to receive support is imprescriptible and never final. Under the Family Code of the Philippines, the amount of child support is determined based on two primary factors: the resources/means of the giver and the necessities of the recipient. Because these factors are subject to change over time—such as the rising cost of living, the child’s educational needs, or an increase in the parent's income—the law allows for the adjustment of support through a petition for increase.

1. Legal Basis for Child Support

Articles 194 to 204 of the Family Code govern the nature and amount of support. Support comprises everything indispensable for sustenance, dwelling, clothing, medical attendance, education, and transportation, in keeping with the financial capacity of the family.

Crucially, Article 202 explicitly states:

"The amount of support... shall be reduced or increased proportionately, according to the reduction or increase of the necessities of the recipient and the resources or means of the person obliged to furnish the same."

2. Valid Grounds for Requesting an Increase

To successfully petition the court for an increase, the petitioner must prove a substantial change in circumstances. Common grounds include:

Increased Needs of the Child: As a child grows, expenses for tuition, extracurricular activities, and medical needs typically rise.
Inflation and Cost of Living: A significant increase in the prices of basic commodities (food, utilities, rent) since the last support order or agreement.
Improved Financial Capacity of the Payor: If the parent providing support has received a significant promotion, a salary increase, or an inheritance, they may be legally required to contribute more.
Special Circumstances: Emergence of chronic health conditions or special educational requirements that were not present when the original amount was set.

3. Methods of Increasing Support

There are two primary ways to effect an increase:

A. Voluntary Agreement (Extrajudicial)

If both parents are on speaking terms, they can enter into a new Compromise Agreement. While this is faster and less adversarial, it is highly recommended to have this agreement notarized and subsequently approved by the court to make it legally demandable and executory.

B. Judicial Petition (Court Action)

If the paying parent refuses to increase the amount voluntarily, the custodial parent must file a Petition for Increase of Support in the Regional Trial Court (Family Court) where the child resides.

4. Procedural Steps in Court

Preparation of the Petition: The custodial parent (Petitioner) works with a lawyer to draft a verified petition detailing the current support, the proposed new amount, and the justifications for the increase.
Filing and Summons: The petition is filed in the Family Court. The court will then issue a summons to the other parent (Respondent).
Pre-trial and Mediation: Courts usually mandate mediation (often through the Philippine Mediation Center) to see if the parties can reach an amicable settlement without a full trial.
Trial/Hearing: If mediation fails, the court will hear evidence. The Petitioner must present receipts, school assessment forms, medical certificates, and evidence of the Respondent’s increased income (if available).
Decision: The judge will issue an Order based on the "Best Interests of the Child" principle.

5. Essential Evidence and Documentation

To prevail in court, the following documents are typically required:

Proof of Child’s Expenses: School tuition receipts, grocery bills, utility bills, and medical prescriptions.
Proof of Petitioner’s Income: To show that the current support is no longer sufficient relative to the custodial parent's earnings.
Proof of Respondent’s Increased Income: Payslips, Income Tax Returns (ITR), or photos of a lifestyle change that suggests higher earnings.
The Previous Order/Agreement: A copy of the original court order or notarized agreement being modified.

6. Important Considerations

Support is not Subject to Waiver: A parent cannot waive the child’s right to future support. Any agreement where a parent "gives up" child support in exchange for something else is generally void.
Provisional Support (Support Pendente Lite): While the case for an increase is ongoing, the court may grant a temporary increase if the need is urgent.
Legal Representation: While some small-claims issues can be handled simply, a formal Petition for Increase of Support in the Family Court requires the services of a licensed attorney to navigate the Rules of Court and the presentation of evidence.