Quick answer

To contest a Bureau of Internal Revenue deficiency assessment, file a valid written administrative protest against the Formal Letter of Demand and Final Assessment Notice (FLD/FAN) within 30 days from receipt—not from the date printed on the notice. State whether you seek reconsideration or reinvestigation, identify the assessment, and dispute every contested issue using supporting facts and legal authorities.

If you choose reinvestigation, submit all relevant supporting documents within 60 days from filing the protest. The BIR generally has 180 days to act. After an adverse final decision—or after the 180-day period expires, if you choose to appeal the inaction—you generally have 30 days to file a petition for review with the Court of Tax Appeals (CTA).

These periods are critical. A late or legally insufficient protest can make the assessment final, executory, and demandable.

Event	Ordinary deadline
Reply to a Preliminary Assessment Notice (PAN)	15 days from receipt
Protest against an FLD/FAN	30 days from receipt
Supporting documents for reinvestigation	60 days from filing the protest
BIR action period	180 days from filing a reconsideration request, or from submission of the required reinvestigation documents
Appeal from an adverse FDDA or other final denial	30 days from receipt
Appeal from BIR inaction, if that option is chosen	30 days after the 180-day period expires

First, identify what the BIR sent

Not every BIR communication is the assessment that must be protested under Section 228 of the National Internal Revenue Code.

Notice of Discrepancy

A Notice of Discrepancy is part of the audit stage. It gives the taxpayer an early opportunity to explain the examiner’s findings and submit records. Under the current audit framework, the notice should clearly identify the alleged discrepancies. Respond promptly, but do not mistake this response for the formal protest required after an FLD/FAN.

Preliminary Assessment Notice

A PAN states the BIR’s preliminary findings. The taxpayer ordinarily has 15 days from receipt to submit a written reply and supporting documents.

A response to the PAN is important, but it does not replace the later protest against the FLD/FAN. The Supreme Court has emphasized that the FLD/FAN—not the PAN—is the assessment that must be administratively protested within 30 days.

Section 228 permits the BIR to issue an FLD/FAN without a PAN in limited cases, including:

A mathematical error apparent on the face of the return;
A discrepancy between tax withheld and tax actually remitted;
An improper carryover of an amount also claimed as a refund or tax credit;
Unpaid excise tax on excisable articles; or
A transfer to a non-exempt person of an article bought or imported by an exempt person.

The absence of a PAN therefore does not automatically invalidate every assessment. The applicable exception and the supporting records must be examined.

Formal Letter of Demand and Final Assessment Notice

The FLD/FAN is the document to protest within 30 days from actual receipt. It should identify the tax type, taxable period, assessed amount, and the facts and law supporting the assessment.

Do not wait for a collection letter, payment deadline, or informal meeting. Negotiations with the examiner do not suspend or replace the statutory protest deadline.

Final Decision on Disputed Assessment

An FDDA communicates the BIR’s decision on the protest. It should state the facts and applicable law, rules, regulations, or jurisprudence supporting the decision and should indicate that it is final.

Treat any communication that unequivocally rejects the protest and finally demands payment as urgent, even if its caption is not “FDDA.” Whether a particular letter constitutes an appealable final decision depends on its wording and context.

How to prepare a valid protest

1. Establish the receipt date immediately

Preserve the evidence showing when and how each notice was received:

The original envelope;
Registry or courier receipts and tracking records;
The registry return card;
Email headers or electronic acknowledgments, if applicable;
The name and position of the person who accepted personal service;
A receiving log, security log, or affidavit concerning delivery; and
A scanned copy of the entire notice, including attachments.

Record separate receipt dates for the PAN, FLD/FAN, and FDDA. Do not calculate the deadline solely from the date printed on a document.

If the business changed address without updating its BIR registration, service at the registered address may create serious problems. Review the service records with counsel instead of assuming that lack of personal knowledge stopped the deadline.

2. Check the audit authority and the assessment process

Obtain and review the Letter of Authority or electronic Letter of Authority (eLA). Confirm:

The taxpayer’s correct name and TIN;
The tax types and taxable periods covered;
The revenue officers specifically authorized;
Whether the officers who conducted the examination were properly authorized;
Whether a replacement or amended authority was issued following a reassignment;
Whether the assessment was issued by an authorized official; and
Whether the audit complied with the current BIR controls.

For audits initiated under the 2026 framework, the general policy is one eLA per taxpayer per taxable year covering the applicable internal revenue taxes, subject to stated exceptions for fraud and certain transactional, event-based, or terminal cases. The authenticity of an LOA may be checked through the BIR website’s Chatbot REVIE LOA Verifier.

An authority or due-process defect may be a substantial defense, but it must be raised properly and supported by the actual documents. Do not ignore an FLD/FAN merely because you believe it is void.

3. Choose reconsideration or reinvestigation expressly

A request for reconsideration asks the BIR to reevaluate the assessment using the records already available, without additional evidence. It may raise factual issues, legal issues, or both. The special 60-day supporting-document period does not apply.

A request for reinvestigation asks for reevaluation using newly discovered or additional evidence that the taxpayer intends to present. The protest must identify that evidence, and all relevant supporting documents must be submitted within 60 days from filing the protest.

If the letter does not clearly request reinvestigation, the BIR may treat it as reconsideration. Choose deliberately. Calling the letter a reconsideration while promising extensive new evidence can create avoidable procedural disputes.

4. Address every disputed issue separately

A bare statement such as “we disagree with the assessment” is unsafe. For every tax type and assessment item, state:

The BIR’s finding and assessed amount;
Whether the entire item or only part is disputed;
The material facts;
The documents proving those facts;
The applicable statutory, regulatory, or jurisprudential basis;
The corrected computation; and
The relief requested.

If an FLD/FAN contains several issues and the taxpayer protests only some of them, the unprotested portions may become final, executory, and demandable. The same risk arises when an issue is nominally disputed but no facts or legal basis are stated for it.

If part of the assessment is accepted, identify it precisely and coordinate payment with the issuing office using the current BIR instructions. Paying the undisputed portion does not require abandoning a properly stated protest against the balance.

5. Include the required identifying information

At minimum, the protest should contain:

Taxpayer’s registered name, TIN, registered address, and contact details;
Assessment notice number and date;
Date the FLD/FAN was received;
Tax types and taxable periods involved;
A clear statement that the letter is a request for reconsideration or reinvestigation;
For reinvestigation, the newly discovered or additional evidence to be submitted;
Separate factual and legal grounds for every disputed issue;
The taxpayer’s proposed corrected computations;
A specific request to cancel or reduce the assessment;
A list of attachments; and
The signature of the taxpayer or properly authorized representative.

Attach the relevant special power of attorney, board resolution, secretary’s certificate, or other proof of authority when appropriate.

6. File with the proper BIR office and obtain proof

Under the BIR’s audit procedures, protest letters and requests for reconsideration or reinvestigation are received by the office of the Regional Director or Assistant Commissioner–Large Taxpayers Service that signed the PAN, FAN, or FLD. Follow the filing instructions and address stated in the assessment.

Submit early enough to correct a receiving-office problem. Obtain a stamped receiving copy showing the date, office, receiving person, and preferably the number of pages and attachments.

Do not assume that sending a protest to the examiner personally, emailing an unofficial address, or handing it to the wrong RDO is sufficient. If using registered mail or a courier, confirm that the method is accepted for the particular filing and preserve proof of dispatch and delivery.

7. Complete a reinvestigation submission within 60 days

For reinvestigation, submit one complete, indexed, and cross-referenced set of supporting documents within the 60-day period. Include a transmittal letter that:

Refers to the original protest;
Identifies every document submitted;
Links each document to a protested issue;
States that the documents constitute the relevant supporting evidence; and
Requests a stamped acknowledgment of the complete submission date.

Late documents may be rejected. Failure to submit the relevant documents within 60 days can result in the assessment becoming final for purposes of challenging its correctness through additional evidence.

Grounds that may justify cancellation or reduction

The available defenses depend on the assessment, returns, books, contracts, and audit history. Common areas for review include:

Factual or computational errors

Examples include duplicated income, taxes paid but not credited, incorrect withholding reconciliation, transposed figures, wrong tax rates, improper allocation, or failure to recognize valid adjustments.

Substantiation disputes

The protest may show that deductions, input VAT, withholding-tax credits, exemptions, or zero-rated transactions were supported by legally sufficient records. The applicable requirements depend on the tax period and the law then in force.

Incorrect legal treatment

The BIR may have characterized a transaction incorrectly, applied the wrong taxable base, ignored a statutory exemption, or used a rule that did not apply during the assessed period.

Lack of valid audit authority

An examination conducted without the required LOA, outside the authority’s stated scope, or by officers not properly authorized may violate due process. The Supreme Court has treated the LOA as an essential safeguard, but the result remains document- and fact-specific.

Prescription

The BIR ordinarily has three years to assess after the return’s statutory or actual filing date, as applicable. Different rules may apply when no return was filed, when a false or fraudulent return was intentionally filed to evade tax, or when the assessment period was validly extended in writing. Review the exact return dates, assessment service date, waivers, and allegations of fraud.

Defective notice or denial

Section 228 requires the taxpayer to be informed in writing of the facts and law supporting the assessment. The implementing regulations impose similar requirements on the FLD/FAN and FDDA. A notice that merely states conclusions without adequately explaining the factual and legal bases may violate due process.

Even when this defense appears strong, file the protest or appeal on time. A taxpayer should not rely on its own declaration that the notice is void.

What happens after the protest

If the BIR grants or partially grants the protest

The BIR may cancel or reduce the assessment. Obtain the formal written disposition and, where applicable, the Authority to Cancel Assessment or other official proof that the disputed amount was removed from the BIR’s records.

If an authorized representative denies the protest

If an FDDA is issued by the Commissioner’s duly authorized representative, the taxpayer generally has 30 days from receipt to choose between:

Filing a petition for review with the CTA; or
Elevating the matter to the Commissioner through a request for reconsideration.

No reinvestigation is available at this administrative-appeal stage, and only the issues covered by the representative’s decision may be entertained. Because the choice affects jurisdiction and later deadlines, obtain tax counsel before selecting the route.

If the Commissioner denies the protest or administrative appeal

File a petition for review with the CTA within 30 days from receipt. A motion asking the Commissioner to reconsider the denial does not suspend the 30-day CTA period.

If the BIR does nothing for 180 days

For a request for reconsideration, the 180-day period is counted from filing the protest. For reinvestigation, it is generally counted from submission of the required documents within the 60-day window.

The taxpayer then has two mutually exclusive options:

Appeal the BIR’s inaction to the CTA within 30 days after the 180-day period expires; or
Wait for the BIR’s final decision and appeal within 30 days after receiving it.

The Supreme Court confirmed this choice in Lascona Land Co., Inc. v. Commissioner of Internal Revenue. Once the taxpayer appeals the inaction, the taxpayer cannot simultaneously follow the wait-for-a-decision route.

If supporting documents were delivered in batches, the start of the 180-day period may be disputed. This is why a complete, indexed submission and an acknowledged completion date are important.

Appealing to the Court of Tax Appeals

An appeal is commenced by a petition for review in the proper CTA Division, ordinarily within the applicable 30-day period. The petition must satisfy the Revised Rules of the CTA, including requirements on jurisdictional allegations, verification, certification against forum shopping, attachments, service, and payment of docket fees.

CTA deadlines are jurisdictional in practical effect. Engage counsel before the administrative period expires so the petition and evidence can be prepared without relying on last-minute relief.

An appeal to the CTA does not automatically suspend collection. If collection may jeopardize the government’s or taxpayer’s interests, the taxpayer may ask the CTA to suspend collection through a verified motion supported by affidavits and documentary evidence. The CTA may require a cash deposit or an acceptable surety bond of not more than twice the disputed amount, although the treatment of a bond depends on the circumstances and legality of the collection method.

Evidence to preserve

Keep a separate assessment file containing:

LOA or eLA and proof of its service;
Verification result from the BIR’s official LOA Verifier;
All notices, schedules, attachments, envelopes, and delivery records;
Tax returns, filing confirmations, and payment records;
Books of accounts and audit trails;
Invoices and other transaction documents;
Withholding certificates and reconciliations;
Financial statements, general ledgers, and subsidiary ledgers;
Contracts, board approvals, and correspondence explaining transactions;
Bank and payment records where relevant;
Copies of every submission to the BIR;
Stamped receiving copies and courier records;
Minutes or written summaries of conferences with BIR personnel; and
A deadline sheet showing each receipt, filing, document-submission, 180-day, and appeal date.

Retain original documents. When providing copies, use an indexed schedule and record exactly what was submitted.

Common mistakes that can lose the case

Treating a PAN response as the protest against the FLD/FAN;
Counting from the notice date instead of proving the receipt date;
Filing only a request for an extension or a one-paragraph objection;
Failing to identify the protest as reconsideration or reinvestigation;
Omitting the assessment date or the applicable legal bases;
Contesting the total amount without addressing each separate issue;
Leaving an assessment item undisputed unintentionally;
Promising additional evidence but missing the 60-day deadline;
Sending the protest only to the revenue examiner;
Relying on an unacknowledged email or undocumented delivery;
Assuming settlement discussions, a compromise application, or partial payment extended a deadline;
Filing another motion with the Commissioner and assuming it suspended the CTA period;
Ignoring a notice because it appears procedurally defective; or
Failing to update the registered address with the BIR.

There is no ordinary automatic extension of the 30-day protest period. A specific law or BIR issuance may occasionally extend deadlines for defined taxpayers affected by an emergency, but do not rely on an extension unless an official issuance clearly covers the taxpayer, office, filing, and due date.

When professional help is urgent

Consult a Philippine tax lawyer and, where needed, a CPA immediately if:

Seven days or less remain in a 15-day or 30-day period;
An FLD/FAN or FDDA involves a substantial amount or several tax types;
The BIR alleges fraud, intentional falsity, or tax evasion;
The notice includes a 50% surcharge or refers to criminal investigation;
A subpoena, warrant of distraint or levy, garnishment, or collection notice has been served;
The assessment concerns several years or related companies;
The assigned revenue officers appear different from those named in the LOA;
The taxpayer denies receiving an earlier notice;
The assessment may already be prescribed;
The BIR began collection before the judicial appeal period expired; or
A CTA petition or motion to suspend collection may be necessary.

Frequently asked questions

Can I protest the PAN instead of waiting for the FAN?

You should reply to the PAN within 15 days, but the statutory administrative protest is directed against the FLD/FAN. If an FLD/FAN is later received, file a separate valid protest within 30 days.

Must I pay before filing an administrative protest?

Ordinarily, no payment of the disputed amount is required merely to file the protest. Any undisputed portion should be identified and paid under the applicable BIR procedure. Interest and other lawful additions may continue to accrue.

Which is better: reconsideration or reinvestigation?

Use reconsideration when the existing record is sufficient. Use reinvestigation when newly discovered or additional evidence is needed. Reinvestigation provides a document-submission opportunity but creates a strict 60-day requirement. The best choice depends on the record and defenses.

Can the BIR extend the 30-day protest deadline?

There is no ordinary discretionary extension under Section 228 and RR No. 18-2013. File within the original period unless a specific official issuance unmistakably grants relief applicable to the case.

Can I file the protest by email?

Do not assume email alone is valid. Follow the assessment’s filing instructions and the procedure of the issuing BIR office. Obtain reliable proof that the correct office received the complete protest on time.

What if the BIR does not act within 180 days?

You may appeal the inaction within the following 30 days or wait for a final decision and appeal within 30 days from receipt. The alternatives are mutually exclusive.

What if I missed the 30-day period?

The assessment may already be final, executory, and demandable. Ordinary arguments about the assessment’s correctness are generally barred. Urgent legal review may still be necessary to examine service, jurisdiction, prescription, a void assessment, or any separate statutory remedy, but relief should not be assumed.

Does this procedure cover local taxes and customs duties?

No. This procedure concerns national internal revenue tax assessments administered by the BIR. Local business taxes, real-property taxes, and customs assessments follow different laws and remedies.

Official legal sources

This article provides general legal information, not legal or tax advice. Outcomes depend on the notices, service records, taxable periods, audit authority, evidence, and procedural history. Official sources and procedures were checked through August 3, 2026.