The Philippine taxation system for individuals is governed primarily by the National Internal Revenue Code of 1997 (NIRC), as amended by Republic Act No. 10963 (Tax Reform for Acceleration and Inclusion or TRAIN Law) and subsequent revenue regulations. The Bureau of Internal Revenue (BIR) administers these provisions through a structured system of tax codes and status classifications. These tools enable precise identification of taxpayers, determination of taxable income scope, applicable rates, withholding obligations, filing requirements, and compliance enforcement. This framework ensures equitable taxation while distinguishing individuals based on citizenship, residency, income sources, and other attributes.

I. The Taxpayer Identification Number (TIN): The Foundational Tax Code

Every individual subject to Philippine income tax or required to file returns must obtain a Taxpayer Identification Number (TIN). This nine-digit code (formatted as XXX-XXX-XXX) serves as the primary and permanent tax identifier for all BIR transactions. It functions as the core “tax code” linking the taxpayer to registration records, returns, payments, withholding certificates, and audits.

Registration occurs through:

BIR Form No. 1902 – for individuals deriving purely compensation income (e.g., employees);
BIR Form No. 1901 – for self-employed persons, professionals, or those engaged in trade or business;
BIR Form No. 1904 – for one-time transactions such as sale of real property or inheritance.

The TIN is mandatory for employment, bank accounts, business permits, real estate dealings, and government transactions. Once issued, it remains unchanged regardless of changes in civil status, address, or income source. Duplicate TINs are prohibited, and violations trigger penalties under Section 236 of the NIRC.

II. Citizenship and Residency-Based Classifications

Section 23 of the NIRC classifies individual taxpayers according to citizenship and residency. This classification dictates the geographical scope of taxable income and the applicable tax regime:

Resident Citizen: A Filipino citizen residing in the Philippines. Taxed on worldwide income at graduated rates under Section 24(A).
Non-Resident Citizen: A Filipino citizen residing and deriving income abroad (including overseas Filipino workers classified as such). Taxed solely on Philippine-source income.
Resident Alien: A foreign national residing in the Philippines for more than 183 days in any calendar year or holding an immigrant or permanent resident visa. Taxed on worldwide income, equivalent to resident citizens.
Non-Resident Alien Engaged in Trade or Business (NRAETB): A foreign national staying in the Philippines for more than 180 days but not qualifying as a resident, and engaged in trade or business. Taxed on Philippine-source income at graduated rates, with possible deductions subject to reciprocity or treaty provisions.
Non-Resident Alien Not Engaged in Trade or Business (NRANETB): Taxed at a flat final rate of 25 percent on gross Philippine-source income (reducible to 15 percent on certain passive incomes such as dividends when applicable under treaties or special laws).

These classifications are determined at registration and must be updated via BIR Form No. 1905 upon any change (e.g., acquisition of permanent residency or relocation abroad).

III. Income Source-Based Classifications

Individuals are further classified by the nature of their income, which affects filing forms, payment schedules, and deduction eligibility:

Pure Compensation Income Earners: Employees receiving salaries, wages, bonuses, and fringe benefits. Subject to withholding tax on compensation under Section 79.
Self-Employed Individuals and Professionals: Persons deriving income from trade, business, or practice of profession (e.g., doctors, lawyers, consultants). Required to pay quarterly estimated taxes and file annual returns.
Mixed Income Earners: Individuals with both compensation and business/professional income. Must segregate income streams for proper taxation and deduction claims.

Additional special classifications include estates and trusts (treated as separate taxable entities but administered by individual fiduciaries) and one-time transaction taxpayers (e.g., sellers of capital assets).

IV. Civil Status and Dependent Classifications: Historical and Current Rules

Civil status is recorded during registration and reflected in official documents, though its tax significance has changed substantially.

Prior to the TRAIN Law (effective January 1, 2018), civil status directly determined personal and additional exemptions under the old Section 35:

Basic personal exemption: ₱50,000 for single, married, or head of family.
Additional exemption: ₱25,000 per qualified dependent child (maximum four).
Withholding tax tables used alphanumeric status codes such as:
- S / ME (single or married with zero qualified dependents)
- S1 / ME1 (one qualified dependent)
- S2 / ME2 (two qualified dependents)
- S3 / ME3 (three qualified dependents)
- S4 / ME4 (four qualified dependents)
- Z (zero exemptions for multiple employers or special cases)

These codes dictated the applicable withholding table column, reducing the taxable base before applying graduated rates.

The TRAIN Law repealed personal and additional exemptions to simplify the system and broaden tax brackets. Civil status and number of dependents no longer reduce taxable income or alter withholding computations. Current withholding tax tables (monthly, semi-monthly, daily) under Revenue Regulations implementing the TRAIN Law are unified and based solely on compensation amount, without reference to status codes. Employers must still record civil status in payroll records and in BIR Form No. 2316 (Certificate of Compensation Payment/Tax Withheld) for informational and statistical purposes.

Civil status categories remain:

Single
Married
Legally separated
Widow or widower

Married couples file separate returns unless one spouse has no income or elects joint filing for administrative convenience. Qualified dependents (children, parents, or other relatives meeting support and age criteria) may still qualify for other benefits outside income tax, such as medical or educational deductions in limited contexts.

V. Alphanumeric Tax Codes (ATC) for Specific Transactions

Beyond the TIN, the BIR employs Alphanumeric Tax Codes (ATC) to classify income types, tax liabilities, and payment categories on returns and remittance forms. These codes ensure accurate crediting and audit trails. Examples relevant to individuals include:

ATC series for withholding tax on compensation (used in monthly remittances via BIR Form No. 1601-C);
ATC for final taxes on passive income (interest, dividends, royalties, prizes);
ATC for capital gains tax (6 percent on real property sales or 15 percent on unlisted shares);
ATC for business income and professional fees in quarterly (Form No. 1701Q) and annual (Form No. 1701) returns;
ATC for one-time transactions (e.g., sale of assets or inheritance).

Taxpayers must select the precise ATC when filing or paying to prevent processing delays or erroneous assessments.

VI. Special Individual Classifications and Incentives

Certain individuals receive tailored treatment:

Overseas Filipino Workers (OFWs): Classified as non-resident citizens when abroad; foreign-sourced income is exempt, but Philippine-sourced income (e.g., bank deposits in the Philippines) remains taxable.
Senior Citizens (Republic Act No. 9994): Entitled to 20 percent discount privileges and tax exemptions on specified purchases; regular income tax rules still apply to earnings.
Persons with Disabilities (PWDs) (Republic Act No. 10754): Similar discounts and incentives; income tax obligations follow standard classification.
Minors: Taxed through parents or guardians unless emancipated; TIN may be obtained under the parent’s or guardian’s registration.

VII. Registration, Updates, and Compliance Obligations

Individuals must register within ten days from commencement of employment, business, or receipt of taxable income. Any change in classification (residency, civil status, business cessation, or death) requires notification via BIR Form No. 1905 within thirty days. Employers register employees and issue Certificates of Compensation (Form No. 2316) annually.

Filing obligations vary by classification:

Pure compensation earners whose taxes were correctly withheld and who have no other income exceeding thresholds are generally exempt from filing an annual income tax return (BIR Form No. 1700).
Self-employed and mixed earners file quarterly (Form No. 1701Q) and annual (Form No. 1701) returns.
Deadlines: April 15 for annual returns; 15th day of the month following each quarter for estimated payments.

Penalties for misclassification, failure to register, late filing, or incorrect ATC usage include surcharges (25 percent or 50 percent for willful neglect), interest (12 percent per annum), and possible criminal liability under Sections 254–255 of the NIRC (fines and imprisonment).

VIII. Applicable Tax Rates by Classification

Resident citizens, resident aliens, and NRAETB: Graduated rates ranging from 0 percent (up to ₱250,000 taxable income) to 35 percent (over ₱8,000,000) post-TRAIN adjustments.
NRANETB: 25 percent final tax on gross income (or lower treaty rates).
Final taxes on passive income, capital gains, and certain winnings apply uniformly regardless of civil status.

Optional standard deduction (40 percent of gross income for self-employed) or itemized deductions remain available where applicable.

This system of tax codes and classifications ensures that every individual’s tax position is clearly defined, accurately assessed, and properly enforced under Philippine law. Compliance with these rules remains mandatory for all covered individuals.