BIR Tax Audit Process in the Philippines: From Letter of Authority (LOA) to Final Assessment

Executive Summary

Receiving a notice from the Bureau of Internal Revenue (BIR) can raise many questions for business owners. Does it mean the company owes additional taxes? What documents must be submitted? Can the business challenge the BIR's findings?

A BIR tax audit is a formal examination of a taxpayer's records to determine whether taxes have been correctly reported and paid.

For many businesses, the process begins with a Letter of Authority (LOA), followed by an examination of accounting records, discussion of discrepancies, and, where warranted, the issuance of assessment notices.

However, not every BIR tax audit results in additional tax liabilities.

Understanding the different stages from the LOA to the Notice of Discrepancy (NOD), Preliminary Assessment Notice (PAN), and Final Assessment Notice (FAN) helps businesses prepare their documents, protect their rights, and respond within the prescribed periods.

This guide explains how the BIR tax audit process works in the Philippines, what businesses should expect, and how to avoid common compliance mistakes.

What Is a BIR Tax Audit?

A BIR tax audit is an examination conducted by authorized revenue officers to verify a taxpayer's compliance with Philippine tax laws.

During the examination, the BIR may review tax returns, audited financial statements, books of accounts, sales invoices, withholding tax records, and other relevant documents.

The objective is to determine whether the taxpayer has properly declared taxable income, reported transactions, claimed deductions, and paid applicable taxes.

For example, the BIR may compare the sales reported in VAT returns with revenue reflected in financial statements.

A difference between these records may require an explanation, but it does not automatically establish that the business has underpaid its taxes.

A tax audit is an examination process, while a tax assessment is the BIR's formal determination of an alleged tax deficiency.

Step-by-Step Guide: Understanding the BIR Tax Audit

Process

Step 1: Issuance of a Letter of Authority (LOA)

The BIR tax audit process generally begins with the issuance of a Letter of Authority or electronic Letter of Authority (eLA).

An LOA authorizes designated revenue officers to examine the taxpayer's books and records for the taxable periods and matters covered by the authority.

Upon receiving an LOA, businesses should verify the taxpayer's information, the authorized revenue officers, the taxable periods covered, and the issuing authority.

The BIR introduced revised audit procedures in 2026, including a single-instance audit framework generally intended to consolidate applicable tax examinations for a taxpayer and taxable year, subject to exceptions. Businesses should review the actual audit authority rather than assume that every examination has the same scope.

Practical tip: Before submitting records, verify the LOA and maintain a record of its receipt.

Step 2: Examination of Books and Accounting Records

After the LOA is issued, authorized revenue officers may request documents relevant to the examination.

These commonly include income tax returns, VAT returns, financial statements, books of accounts, invoices, contracts, withholding tax certificates, and reconciliation schedules.

The BIR may compare information across these records to identify inconsistencies.

Businesses should organize their documents, assign a responsible representative, and maintain copies of everything submitted.

It is also advisable to reconcile financial statements with previously filed tax returns before providing explanations.

Proper preparation can help identify accounting differences early and reduce misunderstandings during the examination.

Step 3: Issuance of a Notice of Discrepancy (NOD)

If the BIR identifies potential differences during the examination, it may issue a Notice of Discrepancy (NOD).

The NOD informs the taxpayer of the discrepancies and provides an opportunity to explain the findings.

For example, the BIR may question differences between declared sales and accounting records, unsupported expenses, or possible withholding tax deficiencies.

At this stage, the taxpayer should review the BIR's computations, prepare supporting documents, and participate in the prescribed discrepancy discussion.

The NOD is not yet a formal tax assessment.

Under the BIR's 2026 audit reforms, discrepancy discussions and taxpayer interactions are subject to documentation and due process safeguards.

Step 4: Issuance of a Preliminary Assessment Notice (PAN)

If the discrepancies remain unresolved, the BIR may issue a Preliminary Assessment Notice (PAN), unless an exception under the law applies.

The PAN generally informs the taxpayer of the proposed deficiency taxes and the factual and legal grounds supporting the findings.

Under the applicable assessment regulations, the taxpayer generally has 15 days from receipt of the PAN to respond in writing.

This is an important opportunity to challenge the proposed assessment before the BIR issues a final assessment.

A response should address the findings individually and explain why the proposed deficiencies are incorrect, unsupported, or require adjustment.

Practical tip: A PAN should not be ignored simply because it is preliminary. Failure to respond can allow the assessment process to proceed without the taxpayer's explanation being fully presented.

Step 5: Issuance of a Final Assessment Notice (FAN)

If the BIR maintains its findings after considering the taxpayer's response, it may issue a Final Assessment Notice (FAN), generally accompanied by a Formal Letter of Demand (FLD).

The FAN formally communicates the alleged deficiency taxes and the basis for the assessment.

Unlike an LOA or NOD, the FAN triggers the administrative protest process.

Under Section 228 of the National Internal Revenue Code, as amended, a taxpayer generally has 30 days from receipt of the assessment to file a valid administrative protest.

The protest may involve a request for reconsideration or reinvestigation, depending on the circumstances.

Failure to file a valid protest within the prescribed period may cause the assessment to become final, executory, and demandable.

Step 6: Administrative Protest and Possible Appeal

If the taxpayer disagrees with the FAN, the next step is generally to file an administrative protest within the prescribed 30-day period.

A request for reconsideration asks the BIR to reevaluate the assessment based on existing records.

A request for reinvestigation involves the submission of additional evidence, with the relevant supporting documents generally required within 60 days from filing the protest.

The BIR must act on the disputed assessment under the applicable rules.

If an appealable decision is issued, the taxpayer may generally seek judicial review before the Court of Tax Appeals (CTA) within 30 days from receipt.

Qualifying BIR inaction may also give rise to a judicial remedy after the applicable 180-day period, subject to the governing rules.

Understanding these deadlines is essential because an otherwise valid defense may be affected by a missed procedural requirement.

BIR Tax Audit Timeline: Important Notices and Deadlines

The following table summarizes the usual stages of a BIR tax examination.

BIR Document or Stage	Purpose	Important Period
Letter of Authority (LOA/eLA)	Authorizes the tax examination	Verify promptly upon receipt
Notice of Discrepancy (NOD)	Communicates preliminary audit discrepancies	Follow the applicable discussion period
Preliminary Assessment Notice (PAN)	Communicates proposed deficiency taxes	Generally 15 days to respond
Final Assessment Notice (FAN)	Formally communicates the tax assessment	Generally 30 days to protest
Administrative protest	Challenges the assessment	60 days for supporting documents in a valid reinvestigation request
BIR decision or qualifying inaction	May lead to CTA review	Generally 30 days to appeal an appealable decision or qualifying inaction

These periods serve different purposes. Taxpayers should always check the applicable rules, the date of receipt, and the specific circumstances of their case.

Risks and Penalties: What Happens if You Ignore a BIR Tax Audit?

Ignoring a lawful BIR examination or failing to respond to assessment notices can create serious financial and legal risks.

Possible Deficiency Taxes and Penalties

If the examination establishes unpaid taxes, the BIR may issue a deficiency assessment.

Depending on the circumstances and applicable law, the liability may include deficiency taxes, surcharges, interest, and other authorized penalties.

The amount will depend on the nature of the tax deficiency, the relevant taxable period, and the applicable statutory provisions.

Loss of the Right to Challenge an Assessment

One of the most serious risks is missing the deadline to protest a Final Assessment Notice.

If a taxpayer fails to file a valid protest within the prescribed period, the assessment may become final, executory, and demandable.

This can significantly limit the taxpayer's ability to dispute the assessment through the ordinary administrative process.

Possible Collection Proceedings

Once a tax assessment becomes final and collectible, the BIR may pursue legally authorized collection remedies, subject to applicable requirements.

These may include distraint, levy, or other collection proceedings permitted under the National Internal Revenue Code.

An LOA or NOD alone does not automatically create a final tax liability. The BIR must comply with the relevant examination and assessment procedures.

Practical Examples

Example 1: Differences Between VAT Returns and Financial Statements

ABC Corporation receives an LOA covering its previous taxable year.

During the examination, the BIR identifies differences between the company's VAT returns and audited financial statements.

The BIR communicates the discrepancies through an NOD.

ABC Corporation reviews its records and prepares a reconciliation showing that some differences arose from accounting adjustments and transactions reported under different tax treatments.

The supporting documents allow the company to explain the discrepancies before the examination proceeds further.

Example 2: Unresolved Withholding Tax Findings

XYZ Corporation undergoes a BIR tax examination involving payments to suppliers.

The BIR identifies possible withholding tax deficiencies and communicates the findings to the company.

XYZ submits supporting documents, but some issues remain unresolved.

The BIR subsequently issues a PAN, where required, identifying the proposed deficiencies.

XYZ must review the notice and submit its response within the applicable period to preserve its opportunity to contest the preliminary findings.

Example 3: A Business Receives a Final Assessment Notice

DEF Corporation receives a FAN assessing additional income tax and withholding tax liabilities.

The company disagrees with the assessment because it believes certain expenses and payments were incorrectly treated.

Rather than ignoring the FAN, DEF files an administrative protest within the prescribed 30-day period and prepares the necessary supporting evidence.

This allows the company to pursue the available administrative remedies under the law.

Frequently Asked Questions

1. Does receiving a BIR Letter of Authority mean my business owes taxes?

No.

An LOA authorizes a tax examination. It does not automatically establish that the business has underpaid taxes.

2. What is the difference between an LOA, NOD, PAN, and FAN?

An LOA authorizes the examination. An NOD communicates discrepancies for discussion. A PAN generally communicates proposed deficiency taxes, while a FAN formally communicates the assessment.

Each document has a different legal purpose and may involve different response requirements.

3. Can the BIR issue a Final Assessment Notice without a PAN?

Yes, in certain circumstances specifically recognized under Section 228 of the National Internal Revenue Code.

However, the BIR must still comply with applicable due process requirements.

4. Can I challenge the BIR's audit findings?

Yes.

Taxpayers may explain discrepancies, submit supporting documents, respond to proposed assessments, and pursue administrative or judicial remedies when permitted by law.

5. How long does a BIR tax audit take?

The duration depends on the complexity of the examination, the records involved, the applicable audit procedures, and the statutory periods.

The BIR generally has three years to assess internal revenue taxes under Section 203 of the National Internal Revenue Code, subject to exceptions and the applicable rules for computing the period.

6. Does a BIR tax audit always result in penalties?

No.

An examination may conclude without a deficiency assessment if no additional tax liability is established.

Penalties arise only when legally applicable.

7. Should businesses engage a CPA or lawyer during a BIR tax audit?

Professional assistance may be valuable when the examination involves complex accounting records, significant transactions, procedural questions, or disputed tax assessments.

A CPA can assist with reconciliations and tax computations, while legal counsel can evaluate taxpayer rights, assessment procedures, and available remedies.

Key Takeaway: Understanding the BIR Audit Process Protects Your Business

A BIR tax audit involves several stages, each with its own purpose and procedural requirements.

From verifying the Letter of Authority to responding to discrepancies and formal assessments, businesses should approach every stage with proper documentation, timely action, and an understanding of their rights.

The most important principle is that an audit finding does not automatically become a final tax liability.

Businesses have opportunities to explain discrepancies and challenge assessments, but those rights must be exercised within the applicable procedures and deadlines.

Call-to-Action: Facing a BIR Tax Audit or Assessment?

Aureada CPA Law Firm provides legal, accounting, and tax advisory assistance to businesses undergoing BIR examinations, tax assessments, and tax disputes.