How to Protest a BIR Tax Assessment

Quick answer

If you receive a Final Assessment Notice and Formal Letter of Demand (FAN/FLD or FLD/FAN) from the Bureau of Internal Revenue (BIR) and disagree with it, you generally have 30 days from receipt to file a written administrative protest. The protest must be either a request for reconsideration or a request for reinvestigation and must comply with the substantive requirements of BIR regulations. Missing the 30-day period can make the assessment final, executory, and demandable.

The key deadlines are different depending on where you are in the assessment process:

Stage	General deadline
Reply to Preliminary Assessment Notice (PAN)	15 days from receipt
Protest against FLD/FAN	30 days from receipt
Supporting documents for a reinvestigation	60 days from filing the protest
BIR period relevant to appeal for inaction	Generally 180 days, with the starting date depending on the kind of protest
Appeal to the Court of Tax Appeals (CTA)	Generally 30 days from the appealable decision or from the applicable lapse of the 180-day period

Under Revenue Regulations No. 18-2013, the 60-day document-submission period applies to a request for reinvestigation, not to a request for reconsideration. A request for reconsideration relies on the records already submitted, while a reinvestigation is based on newly discovered or additional evidence.

These deadlines are strict. Do not assume that negotiations with the revenue officer, an informal request for more time, or continuing discussions with the BIR suspend them.

First determine what BIR document you actually received

Not every BIR communication is protested in the same way.

A Notice of Discrepancy ordinarily arises during the audit or investigation stage. It gives the taxpayer an opportunity to discuss the findings before the formal assessment process advances.

A Preliminary Assessment Notice (PAN) is normally the BIR's proposed deficiency assessment. It should set out the factual and legal bases for the proposed assessment. Under RR No. 18-2013, a taxpayer generally has 15 days from receipt of the PAN to respond. Failure to respond allows the BIR to proceed with an FLD/FAN.

The document that generally triggers the formal 30-day administrative protest period is the Formal Letter of Demand and Final Assessment Notice. The FLD/FAN must state the facts and the law, rules, regulations, or jurisprudence on which the assessment is based; otherwise, Section 228 of the National Internal Revenue Code (NIRC) and the implementing regulations provide that the assessment is void. (Judiciary eLibrary)

An FDDA, or Final Decision on Disputed Assessment, comes later, after the taxpayer has protested the assessment. Receipt of an FDDA can start another critical 30-day period for an administrative appeal to the Commissioner or a judicial appeal to the CTA, depending on who issued the decision and the procedural posture of the case.

Because deadlines normally run from receipt, preserve proof of when and how every assessment notice was delivered.

A PAN is generally required, but there are statutory exceptions

Section 228 ordinarily requires the BIR to notify the taxpayer of its proposed findings before issuing the final assessment. The Tax Code, however, allows the BIR to issue an FLD/FAN without a PAN in specified cases, including when:

1. the deficiency results from a mathematical error apparent on the face of the return;
2. there is a discrepancy between tax withheld and tax actually remitted by a withholding agent;
3. a taxpayer claimed a refund or tax credit of excess creditable withholding tax but also carried over and applied the same amount to succeeding tax liabilities;
4. excise tax on excisable articles has not been paid; or
5. an article purchased or imported by an exempt person is transferred to a non-exempt person under the circumstances covered by the law.

Outside these exceptions, failure to comply with the PAN requirement can raise a serious due-process issue. (Judiciary eLibrary)

How to prepare the 30-day protest

The protest should not merely say that the taxpayer "disagrees" with the assessment.

RR No. 18-2013 requires the written protest to identify the nature of the protest, state the date of the assessment notice, and identify the applicable law, rules and regulations, or jurisprudence on which the protest is based. For a reinvestigation, the protest must also specify the newly discovered or additional evidence the taxpayer intends to present. A protest that fails to comply with these requirements may be treated as void and without force or effect.

Each disputed tax and each disputed adjustment should therefore be addressed separately. For example, if the FLD/FAN contains assessments for income tax, VAT, expanded withholding tax, and withholding tax on compensation, the protest should identify which assessments are disputed and explain the factual and legal grounds for each.

This matters because RR No. 18-2013 provides that an issue not actually disputed may become final, executory, and demandable. The same problem can arise when a taxpayer purports to dispute an issue but fails to state the factual and legal basis for contesting it.

Reconsideration or reinvestigation: which should you choose?

A request for reconsideration asks the BIR to reevaluate the assessment based on the records already submitted. It does not contemplate additional evidence.

A request for reinvestigation asks for reevaluation based on newly discovered or additional evidence that the taxpayer intends to present.

The distinction has procedural consequences.

For a reinvestigation, all relevant supporting documents must generally be submitted within 60 days from filing the protest. RR No. 18-2013 expressly states that this 60-day period does not apply to a request for reconsideration.

The choice also affects when the 180-day period relevant to a possible CTA appeal begins. Under the BIR regulations, the period is generally counted:

• for a reconsideration, from the filing of the protest; and
• for a reinvestigation, from submission of the required supporting documents within the 60-day period.

The choice should therefore be made deliberately. Calling something a "reconsideration" while trying to introduce substantial new evidence later can create procedural problems.

Where and how to file the administrative protest

BIR guidance in RMC No. 15-2020 states that the protest should be addressed to the appropriate Assistant Commissioner, Regional Director, or other authorized higher revenue official and filed with the office of the revenue official that issued the FLD/FAN.

The same guidance allows filing in person or by registered mail. When filed by registered mail, the date of mailing shown by the post-office stamp is treated as the filing date, and the envelope becomes part of the case docket.

For an in-person filing, obtain a clearly dated receiving copy showing the BIR office that received it.

For registered mail, preserve the original registry receipt, tracking information, a copy of the complete protest and attachments, and evidence showing exactly what was mailed.

Do not assume that sending a protest to an individual revenue officer by ordinary email, courier, text message, or messaging application constitutes valid filing unless an applicable BIR issuance expressly authorizes that method for the particular filing.

What should be reviewed before filing the protest?

A tax protest should address both the substance of the alleged deficiency and any legitimate defects affecting the assessment process.

Check the computation

Reconcile the assessment against the returns actually filed, audited financial statements, books of accounts, withholding tax certificates, VAT schedules, invoices, official BIR filings, and other source documents.

Common factual issues include duplicated transactions, timing differences, incorrectly classified expenses, withholding taxes already remitted, income attributed to the wrong taxable period, unreconciled third-party data, or figures taken out of context.

Check whether the legal theory is correct

An adjustment can be mathematically correct but legally wrong. Review the particular NIRC provision, revenue regulation, applicable tax treaty where relevant, and controlling jurisprudence supporting each adjustment.

Check the factual and legal explanation in the PAN and FLD/FAN

Section 228 requires taxpayers to be informed in writing of the facts and law underlying the assessment. Recent Supreme Court decisions continue to treat this as an important due-process requirement. (Judiciary eLibrary)

The question is not simply whether the assessment contains numbers. Whether a notice adequately states its factual and legal bases depends on the contents of the actual assessment documents.

Check the Letter of Authority

Where the assessment arose from a BIR audit, examine the Letter of Authority (LOA) and identify the revenue officers actually conducting the examination.

The Supreme Court has repeatedly held that the authority to examine a taxpayer is not automatically possessed by every revenue officer and that an audit conducted without the required authority, or beyond the authority granted, can result in a void assessment. Whether an LOA defect exists is highly document-specific. (Judiciary eLibrary)

Check prescription

As a general rule, Section 203 of the NIRC gives the BIR three years to assess internal revenue taxes, reckoned under the statutory rules from the applicable return-filing date.

Different rules may apply where there was no return or there was a false or fraudulent return with intent to evade tax. Section 222 provides a 10-year period from discovery in the circumstances specified by that provision. A valid written agreement extending the assessment period can also affect prescription. (Judiciary eLibrary)

Prescription should be calculated separately for the relevant tax return and taxable period. Do not assume that the date of the audit, PAN, or Letter of Authority alone resolves whether the assessment was timely.

What happens after the protest?

If the authorized BIR official denies the protest in whole or in part, the taxpayer ordinarily receives an FDDA.

If the FDDA was issued by the Commissioner's duly authorized representative, RR No. 18-2013 allows the taxpayer, within 30 days from receipt, either to:

• appeal to the Court of Tax Appeals; or
• elevate the matter to the Commissioner through a request for reconsideration.

A reinvestigation is not available at this administrative-appeal stage.

If the Commissioner himself denies the protest or administrative appeal, the taxpayer generally has 30 days from receipt of the decision to appeal to the CTA.

Importantly, RR No. 18-2013 states that filing another motion for reconsideration of the Commissioner's denial does not toll the 30-day CTA appeal period.

What if the BIR does nothing for 180 days?

Inaction does not mean that the taxpayer has won.

When the applicable 180-day period expires without a decision, the taxpayer generally has two alternatives recognized by the Tax Code, CTA Rules, BIR regulations, and Supreme Court jurisprudence.

The taxpayer may appeal the BIR's inaction to the CTA within 30 days after the expiration of the 180-day period.

Alternatively, the taxpayer may wait for the BIR's final decision, even after the 180 days have expired, and then appeal that final decision to the CTA within 30 days from receipt. (Lawphil)

The Supreme Court has emphasized that these remedies are mutually exclusive once the taxpayer chooses one. A taxpayer who files a CTA case based on BIR inaction cannot simultaneously proceed as though still waiting for an administrative decision on the same assessment. (Judiciary eLibrary)

Accurate computation of the 180-day starting date is therefore critical.

The CTA appeal period is especially dangerous to miss

The Court of Tax Appeals has exclusive appellate jurisdiction over decisions of the Commissioner involving disputed BIR assessments and over qualifying instances of BIR inaction. (Lawphil)

A petition for review is generally filed within 30 days from receipt of the appealable decision or, when the taxpayer elects to appeal based on inaction, from expiration of the applicable period fixed by law.

Once the case reaches this point, engage tax litigation counsel promptly. CTA practice involves jurisdictional deadlines, formal pleadings, documentary evidence, judicial affidavits, and procedural rules that are very different from simply sending a protest letter to the BIR.

Does filing a CTA case automatically stop BIR collection?

No.

The CTA law provides that an appeal generally does not automatically suspend the payment, levy, distraint, or sale of property for satisfaction of the tax liability. The CTA may, however, suspend collection when the statutory grounds are established, and it may require the taxpayer to deposit the amount claimed or post a surety bond subject to the limitations provided by law. (Lawphil)

If a warrant of distraint or levy, garnishment, collection letter, or other enforcement action is received while a timely dispute or CTA case is pending, obtain legal advice immediately rather than assuming the pending protest automatically prevents collection.

What evidence should you preserve?

From the moment an audit begins, retain a complete chronological file containing the Letter of Authority and any amendments or replacements; Notice of Discrepancy; PAN and your reply; FLD/FAN and attachments; protest letter; proof of filing; documents submitted in support of a reinvestigation; BIR receiving copies; registered-mail envelopes and registry receipts; emails and formal correspondence; FDDA; collection notices; tax returns; financial statements; books and schedules; invoices and supporting accounting records; and documents identifying the persons who actually received BIR notices.

Proof of receipt dates can determine whether a protest or appeal was timely. Proof of what was actually submitted can determine whether the taxpayer preserved a particular issue.

Common mistakes that can make an assessment much harder to contest

One of the most serious mistakes is protesting the PAN but failing to file a separate protest after receiving the FLD/FAN. A response to the PAN does not replace the statutory protest against the final assessment.

Another is sending a generic letter stating that the taxpayer "strongly disagrees." RR No. 18-2013 requires the protest to identify its nature and provide legal grounds. Issues not properly contested may be treated as undisputed.

Taxpayers also sometimes choose reinvestigation but fail to submit their supporting documents within 60 days, miscalculate the 180-day period, wait after receiving an FDDA without monitoring the 30-day appeal period, or send papers to the wrong BIR office without securing proof of filing.

Another dangerous assumption is that an informal assurance from a revenue officer suspends a statutory deadline. Unless there is a lawful basis for an extension, calculate deadlines from the governing statute and regulations.

Can an assessment still be attacked if the 30-day protest deadline was missed?

The safe rule is to never intentionally miss the deadline. RR No. 18-2013 states that failure to file a valid protest within 30 days ordinarily makes the assessment final, executory, and demandable.

There is, however, an important distinction between an assessment that is merely incorrect and one that is alleged to be void from the beginning.

In the recent Supreme Court decision in Ortiz Memorial Chapel Inc. v. Commissioner of Internal Revenue, G.R. No. 278483, the Court reiterated that an assessment void ab initio for want of fundamental due process produces no legal effect and cannot become valid merely because the taxpayer failed to file a timely protest. (Judiciary eLibrary)

That doctrine should not be treated as a general escape from the 30-day rule. Whether an assessment is truly void is a legal question that depends on the specific defect and the assessment record. An ordinary disagreement over deductions, computations, tax treatment, or evidence normally does not justify simply ignoring the statutory protest process.

What if a deadline falls during a typhoon, government-work suspension, or other force majeure?

Do not automatically assume that the deadline has moved.

Revenue Regulations No. 13-2024 authorizes the Commissioner, in circumstances involving force majeure, to issue appropriate extensions for affected taxpayers and documentary requirements. The BIR has subsequently issued specific circulars extending deadlines for protests and related submissions when covered areas were affected by government-work suspensions. (Bir Cdn)

Whether an extension applies depends on the specific BIR issuance, affected area, affected office, document, and original due date. Check the current BIR issuance applicable to the event rather than relying solely on a news report or announcement that government work was suspended.

Practical action plan after receiving an FLD/FAN

Immediately record the date and manner of receipt. Keep the envelope, courier documentation, receiving stamp, or other evidence.

Calculate the 30-day deadline independently. Do not wait for the revenue officer to tell you when the protest is due.

Obtain the complete assessment docket available to you. At minimum, review the LOA, audit findings, PAN, your PAN response, FLD/FAN, computation schedules, and supporting correspondence.

Prepare an issue-by-issue reconciliation. Separate factual errors, legal disagreements, procedural objections, prescription issues, and evidentiary matters.

Choose reconsideration or reinvestigation deliberately. If additional documents are necessary, account for the 60-day rule applicable to reinvestigation.

File with the proper BIR office and preserve proof of filing.

Calendar every subsequent deadline before submitting the protest. In particular, monitor the relevant 180-day period and any 30-day period triggered by an FDDA or other appealable final decision.

When legal help is urgent

Seek tax counsel immediately if the 30-day protest deadline is approaching; the amount assessed is substantial; fraud or tax-evasion allegations appear in the assessment; the BIR has issued a warrant of distraint or levy, garnishment, or other collection measure; there is a dispute over whether notices were properly served; the Letter of Authority appears defective; prescription may be an issue; the BIR has issued an FDDA; or the 180-day period has expired and you need to decide whether to go to the CTA or await the BIR's decision.

Once a CTA deadline begins to run, waiting until the final days can materially limit the taxpayer's options.

Frequently asked questions

Can I protest a BIR assessment by simply writing that I disagree?

Not safely. The protest must comply with the requirements of RR No. 18-2013, including identifying whether it is a reconsideration or reinvestigation, stating the assessment date, and stating the applicable legal grounds. A reinvestigation must also identify the additional or newly discovered evidence to be presented.

Do I have 60 days to file the protest?

No. The protest against the FLD/FAN is generally due within 30 days from receipt. The separate 60-day period under RR No. 18-2013 concerns submission of supporting documents for a request for reinvestigation.

Does the 60-day supporting-document deadline apply to reconsideration?

Under RR No. 18-2013, no. The regulation expressly states that the 60-day period does not apply to a request for reconsideration.

Can I appeal directly to the CTA after an FDDA?

If the FDDA was issued by the Commissioner's authorized representative, the regulations generally allow either a CTA appeal within 30 days or an administrative request for reconsideration to the Commissioner within the same 30-day period. The proper route should be chosen based on the actual document and procedural history.

What happens if the BIR does not decide my protest within 180 days?

Depending on the type and procedural stage of the protest, you may generally appeal the inaction to the CTA within the following 30 days or wait for the final BIR decision and appeal that decision within 30 days from receipt. Once one of the mutually exclusive remedies is chosen, the taxpayer cannot use the other for the same inaction. (Lawphil)

Does an assessment automatically become valid because I missed the protest deadline?

An ordinary assessment generally becomes final and demandable when no timely valid protest is filed. The Supreme Court has nevertheless recognized that an assessment that is genuinely void ab initio, such as for a fundamental violation of the statutory due-process requirements, cannot acquire validity merely through failure to protest. Whether that narrow exception applies requires examination of the actual assessment documents. (Judiciary eLibrary)

Can the BIR assess taxes from many years ago?

Ordinarily, Section 203 provides a three-year assessment period. Different rules apply to false or fraudulent returns with intent to evade tax, non-filing, valid waivers, and other statutory circumstances. Prescription must therefore be determined from the particular tax, return, taxable period, filing date, assessment date, and any applicable extension or exception. (Judiciary eLibrary)

Official sources

• National Internal Revenue Code, particularly Section 228 on protesting assessments: Supreme Court E-Library — Republic Act No. 8424
• BIR Revenue Regulations No. 18-2013, amending the assessment and protest rules under RR No. 12-99: BIR — Revenue Regulations No. 18-2013
• BIR guidance on responding to deficiency assessments and filing administrative protests: BIR — RMC No. 15-2020 Annex A
• Court of Tax Appeals jurisdiction and official resources: Court of Tax Appeals
• Revised Rules of the Court of Tax Appeals: Lawphil — A.M. No. 05-11-07-CTA
• Republic Act No. 9282 on CTA jurisdiction over disputed assessments and BIR inaction: Lawphil — Republic Act No. 9282

General-information disclaimer

This article provides general Philippine legal information and is not a substitute for advice based on the actual PAN, FLD/FAN, FDDA, Letter of Authority, tax returns, audit records, proof of service, and procedural history of a particular case. Tax-assessment deadlines can be jurisdictional or otherwise result in an assessment becoming final, so taxpayers facing an active assessment should obtain advice promptly.

Sources and current-law status checked: 23 August 2026.