In the Philippine labor landscape, the classification of an employee as "part-time" does not exempt the employer or the employee from the mandatory contributions required by law. Under the Labor Code of the Philippines and specific social legislation, all employees—regardless of their status (regular, casual, project-based, or part-time)—are entitled to social security protections.

The three primary agencies governing these deductions are the Social Security System (SSS), the Philippine Health Insurance Corporation (PhilHealth), and the Home Development Mutual Fund (Pag-IBIG Fund).

I. The Social Security System (SSS)

The SSS provides replacement income for workers in the event of disability, sickness, maternity, old age, and death.

Mandatory Coverage: Section 9 of Republic Act No. 11199 (The Social Security Act of 2018) states that coverage in the SSS shall be compulsory upon all employees not over sixty (60) years of age and their employers.
Basis of Deduction: Contributions are based on the employee's Monthly Salary Credit (MSC). For part-time workers, the MSC is determined by their actual gross income for the month.
Contribution Rate: As of the current schedule, the total contribution rate is 14% of the MSC. This is shared between the employer (9.5%) and the employee (4.5%).
Effect of Part-Time Status: If a part-time worker earns less than the minimum MSC, they are still required to contribute based on the lowest tier of the SSS contribution table.

II. Philippine Health Insurance Corporation (PhilHealth)

PhilHealth provides health insurance coverage and ensures affordable health care services for all Filipinos.

Universal Health Care (UHC) Act: Under Republic Act No. 11223, all Filipino citizens are automatically enrolled in the National Health Insurance Program.
Premium Rates: The premium rate for "Direct Contributors" (which includes part-time employees) has been incrementally increasing toward a 5% ceiling.
The Salary Floor and Ceiling: PhilHealth implements a "monthly basic salary" floor and ceiling. If a part-time employee’s monthly salary falls below the floor, the deduction is calculated based on that minimum floor.
Sharing: The premium is divided equally (50/50) between the employer and the employee.

III. Home Development Mutual Fund (Pag-IBIG Fund)

Commonly known as the Pag-IBIG Fund, this agency focuses on national savings and affordable shelter financing.

Mandatory Membership: Republic Act No. 9679 mandates Pag-IBIG coverage for all employees covered by the SSS.
Contribution Rates:
- For those earning ₱1,500 or less per month: 1% (Employee) and 2% (Employer).
- For those earning over ₱1,500 per month: 2% (Employee) and 2% (Employer).
Maximum Contribution: The maximum monthly compensation used for computing contributions is currently capped at ₱10,000 (unless higher voluntary contributions are agreed upon). This means the standard maximum mandatory deduction for an employee is ₱200, matched by ₱200 from the employer.

IV. Key Legal Principles for Part-Time Arrangements

1. Pro-Rata Application

While the rates of deduction are fixed by law, the amount deducted from a part-time employee is naturally lower than that of a full-time employee because it is a percentage of their actual gross monthly earnings (subject to the minimum floors of each agency).

2. Multiple Employers

It is common for part-time employees to work for more than one employer. In such cases:

SSS: The employee must be reported by all employers. Each employer will deduct the corresponding employee share and pay the employer share based on the compensation paid by that specific firm.
PhilHealth/Pag-IBIG: Similar to the SSS, each employer is responsible for deducting and remitting contributions based on the specific salary they pay the worker.

3. Tax Treatment (Withholding Tax)

Under the TRAIN Law (Republic Act No. 10963), employees—including part-time workers—earning an annual gross income of ₱250,000 or below are exempt from personal income tax. Since many part-time positions fall below this threshold, they may have zero withholding tax. However, the employer is still required to file the necessary BIR forms to reflect the employee's status.

4. The "No Contribution, No Benefit" Rule

Employers are legally prohibited from deducting the employer's share of the contribution from the employee's wages. Article 116 of the Labor Code prohibits the withholding of wages, and specific social security laws impose criminal liability on employers who fail to remit both the deducted employee share and the mandated employer share.

V. Compliance and Penalties

Failure to deduct and remit these contributions constitutes a violation of Philippine law. Employers may face:

Interest: Typically 2-3% per month for late remittances.
Fines: Substantial monetary penalties.
Imprisonment: Executives or owners can face jail time for non-remittance of SSS, PhilHealth, or Pag-IBIG funds, as these are considered "trust funds" held for the benefit of the worker.