Quick answer

To contest a BIR deficiency assessment, file a valid written administrative protest within 30 days from receipt of the Formal Letter of Demand and Final Assessment Notice (FLD/FAN). State whether you are requesting:

Reconsideration — re-evaluation based on records already available to the BIR; or
Reinvestigation — re-evaluation using newly discovered or additional evidence.

Identify the assessment date, address every disputed issue separately, and state the supporting facts and legal authorities. A vague letter saying only that you “disagree” may be treated as void. If you choose reinvestigation, submit all relevant supporting documents within 60 days from filing the protest.

If the protest is denied, or the BIR does not act within the applicable 180-day period, a petition for review may be filed with the Court of Tax Appeals (CTA), generally within 30 days from receipt of the denial or from expiration of the 180-day period. These are strict deadlines. Record the exact date and manner in which every notice was received.

The controlling framework is Section 228 of the National Internal Revenue Code, implemented principally by Revenue Regulations No. 18-2013.

First identify what document you received

Not every BIR audit letter is a final assessment. The available response and deadline depend on the document.

Document	What it generally means	Immediate action
Notice of Discrepancy or notice for informal conference	The audit is still at an early stage	Present explanations and records promptly. Under RR No. 7-2018, the informal conference generally cannot extend beyond 30 days from receipt of the notice.
Preliminary Assessment Notice (PAN)	The BIR proposes deficiency taxes	Respond within 15 days from receipt. A PAN response is not the formal protest against an assessment, but it is an important opportunity to correct the findings.
FLD/FAN	The BIR has made a formal assessment and demanded payment	File a valid reconsideration or reinvestigation request within 30 days from receipt.
Final Decision on Disputed Assessment (FDDA)	The BIR has ruled on the protest	Determine immediately whether to appeal administratively to the CIR, when allowed, or file a petition for review with the CTA within 30 days.
Collection letter, Final Notice Before Seizure, warrant of distraint or levy, or garnishment notice	Collection action may be underway	Obtain tax litigation advice immediately. The document may affect the period for judicial relief, depending on the case history and its contents.

A response to the PAN does not replace the protest required after receipt of the FLD/FAN. Conversely, do not wait for a collection notice before protesting a FAN.

Responding to the PAN

A PAN should explain in detail the facts and the law, regulations, or jurisprudence supporting each proposed deficiency. The taxpayer normally has 15 days from receipt to respond.

The BIR’s RMO No. 26-2016 describes a PAN response as optional in the sense that failing to submit one does not eliminate the later right to protest a timely received FLD/FAN. Nevertheless, silence allows the assessment process to proceed without the taxpayer’s explanation.

A useful PAN response should:

Match each objection to the corresponding audit finding.
Correct factual assumptions and computations.
Cite the return, invoice, withholding certificate, contract, ledger entry, or other record proving the correction.
Identify legal objections, including the applicable tax period and version of the law.
State any objection concerning the authority or scope of the audit, service of notices, prescription, or lack of factual and legal basis.
Attach an indexed set of supporting documents and retain proof of submission.

A PAN is generally required, but Section 228 allows an FLD/FAN to be issued without one in these situations:

A mathematical error appears on the face of the return.
Tax withheld differs from the amount remitted by the withholding agent.
An excess creditable withholding tax was both claimed for refund or tax credit and carried over to the succeeding taxable period.
Excise tax on excisable articles was not paid.
An article bought or imported by an exempt person was transferred to a non-exempt person.

The absence of a PAN therefore does not automatically invalidate every assessment. First determine whether a statutory exception applies.

The 30-day protest against the FLD/FAN

The formal protest must be filed within 30 days from actual receipt of the FLD/FAN. Failure to file a valid and timely protest generally makes the assessment final, executory, and demandable.

Under RMC No. 11-2014, the protest should be filed with the duly authorized representative of the Commissioner who signed the PAN and FLD/FAN. Follow the filing instructions stated in the notice. If the office gives different oral instructions, request written confirmation.

File early enough to correct a rejected or misdirected submission before the deadline. Obtain a stamped receiving copy or another reliable official acknowledgment showing:

Filing date and time;
Receiving office;
Name or identification of the receiving personnel;
Number of pages and attachments; and
Assessment number and taxable periods covered.

Do not rely only on an unacknowledged email, ordinary delivery, or a verbal assurance that the protest was received.

Choosing reconsideration or reinvestigation

Request for reconsideration

Choose reconsideration when the protest can be decided using records already available to the BIR and no new evidence needs to be presented. It may raise factual issues, legal issues, or both.

The 60-day document-submission period does not apply to reconsideration. The BIR’s 180-day period to act is generally counted from filing of the reconsideration request.

Request for reinvestigation

Choose reinvestigation when you need to submit newly discovered or additional evidence. The protest must identify the evidence you intend to present.

All relevant supporting documents must be submitted within 60 days from filing the protest. The regulation treats this period strictly. Evaluation may be limited to documents submitted on time.

For a reinvestigation, the BIR’s 180-day period generally begins from submission of the required supporting documents within the 60-day period. Obtain a received copy of the transmittal and a complete inventory of every attachment because that submission date may determine the CTA deadline.

Do not label a protest “reconsideration” merely to avoid the 60-day deadline if the argument actually depends on new documents. Equally, do not request reinvestigation when all necessary records are already in the BIR file without considering the additional documentary burden and the different starting point for the 180-day period.

What a valid protest should contain

At minimum, the protest should clearly state:

The taxpayer’s legal name, TIN, registered address, and contact details.
The assessment number, tax types, taxable periods, and date of the FLD/FAN.
The date and manner in which the FLD/FAN was received.
Whether the protest is a request for reconsideration or reinvestigation.
If reinvestigation is requested, the newly discovered or additional evidence to be submitted.
Whether the entire assessment or only specified portions are disputed.
For every disputed issue:
- The BIR finding;
- The amount disputed;
- The material facts;
- The taxpayer’s explanation;
- The applicable statute, regulation, or jurisprudence; and
- The supporting evidence.
The specific relief requested, such as cancellation or reduction of the assessment and related penalties.
A numbered list of attachments.
The taxpayer’s or authorized representative’s signature and proof of authority.

The regulations require the protest to state its nature, the assessment date, and the applicable legal authorities. Failure to satisfy these requirements may make the protest void. The Supreme Court enforced these requirements in CIR v. Citysuper, Inc..

If several issues are assessed, address each one. An issue not disputed, or not supported by facts and legal grounds, may be treated as undisputed. The corresponding portion can become final and collectible even while other issues remain under protest.

Review the assessment for procedural and substantive defects

A protest should not rely only on a recalculation. Review the complete assessment record.

Written factual and legal basis

The PAN and FLD/FAN must sufficiently explain the factual and legal grounds for the assessment. A table of figures or general statutory citation may be inadequate if it does not enable the taxpayer to prepare an intelligent protest.

The Supreme Court has repeatedly treated this as a substantive due-process requirement. See CIR v. Avon Products Manufacturing, Inc. and CIR v. Spouses Magaan. Whether a particular explanation is sufficient depends on the complete notices and written exchanges, so the actual documents must be reviewed.

Proper service and actual receipt

Service may be personal, substituted, or by mail or professional courier under the conditions in RR No. 18-2013. Service on a properly appointed tax agent may be treated as service on the taxpayer.

Preserve the envelope, registry notice, courier record, receiving log, and the identity and authority of the person who accepted the notice. If receipt is genuinely disputed, service becomes an evidentiary issue. The Supreme Court discussed the BIR’s burden to prove proper service when receipt is denied in CIR v. Heirs of Chit S. Lhuillier.

Assessment period

As a general rule, the BIR must assess within three years from the statutory filing date or the actual filing date when the return was filed late. Important exceptions include failure to file a return and a false or fraudulent return with intent to evade tax, for which a 10-year period from discovery may apply. A valid written waiver may also affect the period.

Prescription analysis is document- and date-sensitive. Review the return, filing confirmation, Letter of Authority, waivers, PAN, FLD/FAN, mailing or service evidence, and any suspension events before asserting that the assessment was late.

Authority, scope, tax base, and penalties

Other possible issues include:

Whether the audit was performed by properly authorized officers and within the authority granted;
Whether the assessed transaction, income, deduction, withholding, or input tax was correctly characterized;
Whether the correct law and tax rate for the specific taxable period were used;
Whether payments, credits, and withholding certificates were recognized;
Whether the BIR used unsupported assumptions or duplicated amounts;
Whether surcharges, interest, and compromise penalties were legally and mathematically proper; and
Whether the BIR considered the taxpayer’s explanations and evidence.

These are possible areas for examination, not automatic grounds for cancellation.

What happens after the protest

If an authorized representative denies the protest

When an FDDA is issued by the Commissioner’s duly authorized representative, the taxpayer may generally choose, within 30 days from receipt, to:

File a petition for review with the CTA; or
Elevate the matter to the Commissioner of Internal Revenue through a request for reconsideration.

An administrative appeal to the Commissioner cannot be a reinvestigation. Only issues raised in the authorized representative’s decision may be entertained under RR No. 18-2013.

If the Commissioner denies the protest or administrative appeal

File a petition for review with the CTA within 30 days from receipt. A further motion for reconsideration filed with the Commissioner does not suspend or restart the 30-day CTA period.

The FDDA should state the facts and legal authorities supporting the decision and indicate that it is the final decision. However, do not simply disregard a collection letter or other adverse communication because it is not titled “FDDA.” Its wording and the case history may show that it is the BIR’s final action.

What if the BIR does nothing for 180 days?

The applicable 180-day period is generally counted:

From filing of the protest for a request for reconsideration; or
From submission of the required supporting documents for a request for reinvestigation.

After the 180 days expire without action, the taxpayer has two mutually exclusive options:

Appeal the BIR’s inaction: File a petition for review with the CTA within 30 days after expiration of the 180-day period; or
Wait for the BIR’s final decision: Appeal that eventual decision within 30 days from receipt.

The Supreme Court confirmed these alternatives in Lascona Land Co., Inc. v. CIR and reiterated them in Light Rail Transit Authority v. BIR.

Once the taxpayer attempts to use the inaction route, an untimely CTA petition cannot ordinarily be repaired by switching to the wait-for-a-decision route. Maintain a written deadline calendar showing the protest date, document-submission date, end of the 180 days, and end of the following 30 days.

Appealing to the Court of Tax Appeals

An appeal is made through a petition for review before the CTA Division under the Revised Rules of the Court of Tax Appeals. The 30-day appeal period is jurisdictional and is treated strictly.

A CTA case requires more than forwarding the protest letter. The petition must properly allege jurisdiction and material dates, state the facts and issues, attach the challenged assessment and decision or proof of inaction, comply with verification and certification requirements, pay the required fees, and follow current filing and service rules. Engage Philippine tax litigation counsel well before the deadline, particularly for a corporation or a case involving substantial exposure.

Do not assume that filing an administrative or judicial appeal automatically stops collection. Under Section 11 of Republic Act No. 1125, as amended by RA No. 9282, a CTA appeal generally does not suspend payment, levy, distraint, or sale. The CTA may suspend collection when the statutory conditions are met and may require a cash deposit or surety bond of not more than twice the amount claimed.

Evidence to preserve

Keep both originals and secure electronic copies of:

The Letter of Authority and any amendments or replacement authority;
Notices of Discrepancy and informal-conference records;
PAN, FLD/FAN, FDDA, and all collection notices;
Envelopes, registry receipts, return cards, courier tracking, and receiving logs;
Tax returns, filing confirmations, payment receipts, and withholding certificates;
Books, ledgers, invoices, official receipts, contracts, bank records, and reconciliations;
Audit schedules, computations, working papers, and document requests;
Every protest, response, transmittal, annex, and proof of BIR receipt;
Emails, letters, meeting minutes, and notes of material communications;
Waivers of the statute of limitations and proof concerning their execution;
Corporate resolutions, special powers of attorney, and other proof of representative authority; and
A dated chronology of the audit, notices, filings, and decisions.

Preserve records in their original form. Avoid altering metadata, writing over original documents, or surrendering the only copy without a complete receipt and duplicate.

Common mistakes

Treating the PAN response as the protest against the FAN.
Counting the deadline from when management or outside counsel first saw the notice instead of its legally relevant receipt.
Filing a generic objection without facts and legal grounds for every assessment issue.
Failing to specify reconsideration or reinvestigation.
Requesting reinvestigation but missing the 60-day supporting-document deadline.
Sending documents without a complete transmittal and proof of receipt.
Filing with an investigating officer instead of the office identified by the governing rules and notice.
Leaving some tax types or issues unchallenged unintentionally.
Assuming meetings or follow-up letters extend statutory deadlines.
Filing another motion with the Commissioner after a CIR denial and assuming it pauses the CTA period.
Appealing the 180-day inaction late and then attempting to wait for another decision.
Assuming that a protest or CTA appeal automatically suspends collection.
Ignoring notices delivered to the registered address or an appointed tax agent.
Relying on an oral promise that collection will be held in abeyance.

When legal help is urgent

Seek Philippine tax counsel immediately if:

Fewer than 10 days remain before a protest or CTA deadline;
An FDDA or collection notice has been received;
The BIR has issued or threatened garnishment, distraint, levy, or sale;
Receipt or service of an assessment is disputed;
The assessment alleges fraud, falsity, willful failure, or criminal conduct;
Important records are missing or held by another person;
The amount is significant enough to threaten operations or personal assets;
A waiver of the assessment period was signed;
The BIR is applying the 10-year assessment period;
A deadline may already have been missed; or
Suspension of collection may need to be requested from the CTA.

Frequently asked questions

Do I have to pay the assessment before filing a protest?

Section 228 does not generally require full prepayment as a condition for filing the administrative protest. However, applicable interest may continue, undisputed portions can become collectible, and a later CTA appeal does not automatically suspend collection.

Can I protest only part of the assessment?

Yes. Clearly identify the disputed and accepted portions. An undisputed issue or amount may become final, executory, and demandable.

Can the 30-day or 60-day deadline be extended?

Treat both as mandatory and non-extendible. Occasionally, the BIR issues written deadline relief for specified emergencies, locations, taxpayers, or dates. Rely on such relief only when an official issuance clearly covers the particular filing.

What if I received only a PAN?

Respond within 15 days, but continue monitoring for the FLD/FAN. If an FLD/FAN is later received, file the separate formal protest within 30 days.

Which is better: reconsideration or reinvestigation?

Neither is universally better. Reconsideration fits a case that can be resolved from existing records. Reinvestigation fits a case requiring additional evidence but carries a strict 60-day document deadline. The correct choice depends on what the BIR already has and what must still be proven.

What if the BIR never decides my protest?

After the applicable 180 days, either appeal the inaction to the CTA within the next 30 days or wait for a final BIR decision and appeal within 30 days from its receipt. Do not combine the two routes.

Does an invalid assessment need to be protested?

Do not assume that an alleged defect eliminates the need to protest. File a timely protest preserving the procedural objection and all alternative factual and legal defenses. Failure to protest can severely restrict later remedies.

What if the 30-day protest deadline has already passed?

The assessment will ordinarily be treated as final, executory, and demandable. Obtain urgent advice to examine actual service, the nature of the document, jurisdictional or due-process defects, prescription, and any collection remedies. Do not assume that a new letter automatically reopens the assessment.

Official legal sources

This article provides general legal information, not legal or tax advice for a particular assessment. Outcomes and deadlines can depend on the notices, service records, taxable periods, and procedural history. Official sources were checked as of August 4, 2026.