Quick answer

To dispute a BIR 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. Address every disputed issue, identify whether the protest is a request for reconsideration or request for reinvestigation, and state the supporting facts and legal authorities.

If you choose reinvestigation, submit all relevant supporting documents within 60 days from filing the protest. Missing the applicable deadline can make the assessment final, executory, and demandable. These periods should be treated as mandatory and non-extendible.

Do not confuse a reply to a Preliminary Assessment Notice (PAN) with the required protest against the later FLD/FAN. A PAN reply does not preserve your right to contest a final assessment.

Know which BIR document you received

The correct response depends on the document.

Notice of Discrepancy

A Notice of Discrepancy is part of the pre-assessment process. It gives the taxpayer an opportunity to explain audit findings before a proposed assessment is issued. Respond promptly according to the notice, but remember that it is not yet the final assessment contemplated by Section 228 of the Tax Code.

Preliminary Assessment Notice

A PAN states the BIR’s proposed deficiency findings. Under Revenue Regulations No. 18-2013, the taxpayer generally has 15 days from receipt to respond.

The BIR may issue an FLD/FAN without a PAN when:

The deficiency results from a mathematical error appearing on the face of the return;
There is a discrepancy between tax withheld and tax actually remitted;
An amount claimed as a refund or tax credit for excess creditable withholding tax was also carried over and applied to the succeeding taxable year;
Excise tax on excisable articles was not paid; or
An article acquired tax-free by an exempt person was sold, traded, or transferred to a non-exempt person.

Even if you answered the PAN, you must separately protest the FLD/FAN if the BIR proceeds with the assessment. The Supreme Court has emphasized that, as a general rule, it is the FLD/FAN—not the PAN—that must be administratively protested within 30 days. See CIR v. Liquigaz Philippines Corporation.

Formal Letter of Demand and Final Assessment Notice

The FLD/FAN is the formal assessment and demand for payment. This is the usual trigger for the 30-day protest period.

Record immediately:

The exact date and manner of receipt;
Who received the notice;
Every assessment number;
The tax type and taxable period;
The basic tax, surcharge, interest, and other amounts claimed; and
The name and position of the official who signed the notice.

Service on an appointed tax agent or practitioner may be treated as service on the taxpayer. A notice may also be served personally, by substituted service, registered mail, or another mode permitted by the applicable regulations. Do not calculate the deadline from the date printed on the notice when the controlling rule is receipt—but preserve proof of the actual receipt date.

The critical deadlines

Stage	Required action	General deadline
PAN	Submit a written response	15 days from receipt
FLD/FAN	File a valid request for reconsideration or reinvestigation	30 days from receipt
Reinvestigation	Submit all relevant supporting documents	60 days from filing the protest
BIR inaction	Appeal the inaction to the CTA, if choosing that remedy	Within 30 days after the applicable 180-day period expires
Denial by an authorized BIR representative	Appeal to the CTA or elevate the protest to the Commissioner	30 days from receipt
Denial by the Commissioner	File a petition for review with the CTA	30 days from receipt

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

File early. Do not assume that a request for an extension, an informal discussion with an examiner, a settlement proposal, or a motion asking the BIR to reconsider will stop a statutory period.

Choose the correct type of protest

Request for reconsideration

A request for reconsideration asks the BIR to re-evaluate the assessment using the records already available. It can raise factual or legal questions, but it does not depend on newly discovered or additional evidence.

This is usually appropriate when:

The necessary evidence is already in the BIR’s audit file;
The dispute concerns the interpretation or application of law;
The assessment contains a legal or computational error apparent from existing records; or
No additional documents are needed to establish the taxpayer’s position.

The separate 60-day document-submission period does not apply to reconsideration under Revenue Regulations No. 18-2013. Nevertheless, attach or clearly identify the existing records on which you rely.

Request for reinvestigation

A request for reinvestigation asks the BIR to re-evaluate the assessment using newly discovered or additional evidence. The protest must specify the evidence you intend to submit.

This is usually appropriate when additional records are needed, such as:

Reconciliations and transaction schedules;
Contracts and amendments;
Invoices, receipts, and proof of payment;
Withholding tax certificates;
Importation or export documents;
Bank records;
General-ledger details and journal entries;
Confirmations from customers, suppliers, or related parties; or
Affidavits explaining material facts.

All relevant supporting documents must be submitted within 60 days from filing the protest. Prepare as if the deadline will not be extended. BIR guidance states that late documents may be rejected and a missed deadline may result in finality or denial of the assessment protest. See Revenue Memorandum Order No. 26-2016.

A protest that does not clearly request reinvestigation may be treated as a request for reconsideration. State the chosen remedy expressly.

What a valid protest should contain

A bare statement that you disagree, a request for more time, or a general reservation of rights is dangerous. The Supreme Court has upheld the consequences of failing to comply with the specific requirements of Revenue Regulations No. 18-2013. See CIR v. V.Y. Domingo Jewellers, Inc..

A careful protest should contain:

Taxpayer identification

State the taxpayer’s registered name, TIN, registered address, contact details, and the authority of the person signing.
Identification of the assessment

List the date of the FLD/FAN, assessment numbers, taxable periods, tax types, and date of receipt.
Express nature of the protest

State prominently whether it is a request for reconsideration or reinvestigation. If reinvestigation is requested, identify the additional evidence to be presented.
Scope of the protest

State whether the entire assessment or only specified portions are disputed. Identify the exact amount contested for each tax type and issue.
Issue-by-issue factual discussion

Answer each BIR finding separately. Explain what occurred, identify the relevant transactions, and reconcile the taxpayer’s records with the assessment.
Legal basis

Cite the applicable Tax Code provisions, regulations, controlling jurisprudence, or other governing law for every disputed issue. Do not rely only on broad claims such as “the assessment is unfair” or “the books are correct.”
Supporting evidence

Mark, index, and cross-reference each attachment. For voluminous records, provide understandable schedules tied to the underlying documents and accounting entries.
Relief requested

Ask for cancellation or reduction of the assessment, correction of the computation, or another specific result supported by the protest.
Signature and authority

Have the taxpayer or properly authorized representative sign. Include the appropriate authorization document, such as a special power of attorney, board authorization, or proof of the representative’s authority, when applicable.
List of attachments

Include a complete annex index and state the number of pages or files submitted.

If the FLD/FAN contains several issues and the protest fails to dispute an issue with supporting facts and legal authority, the BIR may treat that issue as undisputed. The tax attributable to undisputed issues may become final and collectible.

Where and how to file

File the protest with the duly authorized representative of the Commissioner who signed the FLD/FAN. BIR guidance specifically directs taxpayers to submit the protest to that official’s office. See Revenue Memorandum Circular No. 11-2014.

Before the deadline:

Confirm the responsible office from the notice and the signatory;
Confirm directly with that office which filing methods it currently accepts;
Do not assume that ordinary email, an upload to a general BIR facility, or delivery to a different RDO constitutes valid filing;
Obtain a date-stamped receiving copy showing the office, recipient, date, and attachments received;
If an officially accepted mail or courier method is used, preserve the registry or courier receipt, tracking history, proof of delivery, and a complete copy of the package;
Submit a cover letter and annex inventory; and
Preserve proof that the signatory was authorized to act for the taxpayer.

The BIR has identified filing with the wrong office, late filing, failure to state legal grounds, and failure to specify additional evidence for reinvestigation as circumstances that can make a protest invalid. See Revenue Memorandum Circular No. 11-2020.

Review both the merits and the assessment procedure

A protest should ordinarily address the substantive tax findings and any procedural defects. Potential issues include the following, but their effect depends on the complete audit record.

Lack of adequate factual or legal basis

Section 228 requires the taxpayer to be informed in writing of the facts and law on which the assessment is based. Revenue Regulations No. 18-2013 likewise require the FLD/FAN and the Final Decision on Disputed Assessment to state their factual and legal bases.

The Supreme Court has treated this as an important due-process requirement. See CIR v. Avon Products Manufacturing, Inc. and CIR v. Yumex Philippines Corporation.

A procedural defect does not justify ignoring the notice. Raise the defect within the deadline and address the merits where possible. Whether the defect invalidates the assessment, only the decision, or neither will depend on the documents and circumstances.

Failure to issue a required PAN

Check whether a PAN was served and whether one of the statutory exceptions applied. Also check whether the PAN stated the factual and legal grounds in sufficient detail and whether the taxpayer was given the required opportunity to respond.

Prescription

As a general rule, internal revenue taxes must be assessed within three years after the last day prescribed for filing the return. If a return was filed late, the period is generally counted from actual filing; a return filed early is treated as filed on the statutory due date.

Different rules may apply to a false or fraudulent return made with intent to evade tax, failure to file a return, valid written waivers, and other statutory circumstances. For a false or fraudulent return with intent to evade tax or failure to file, Section 222 generally provides a 10-year period from discovery. Prescription analysis is document- and date-sensitive: obtain the returns, filing confirmations, waivers, notices, and proof of service before reaching a conclusion.

Audit authority and scope

Review the Letter of Authority or other audit instrument, the officers named, taxable period, covered taxes, dates of reassignment or replacement, and authority of the officials who issued the assessment. Current BIR audit procedures include electronic Letters of Authority and revised controls under Revenue Memorandum Order No. 1-2026. The legal effect of an alleged authority defect depends on the particular instrument and controlling jurisprudence.

Incorrect facts or computations

Reconcile the assessment against the returns, books, financial statements, invoices, withholding certificates, and third-party information relied upon by the BIR. Trace every disputed amount to source records. Check the taxable base, tax rate applicable to the period, credits, prior payments, surcharge, and interest computation.

Failure to consider the taxpayer’s evidence

Identify evidence previously submitted and show when and how the BIR received it. Attach the receiving copy, transmittal, or other proof. Explain precisely how that evidence answers the assessment.

What happens after filing

If an authorized representative denies the protest

If the protest is wholly or partly denied by the Commissioner’s duly authorized representative, the taxpayer generally has two alternatives within 30 days from receipt:

File a petition for review with the Court of Tax Appeals; or
Elevate the protest to the Commissioner through a request for reconsideration.

An administrative appeal to the Commissioner cannot be a new request for reinvestigation. Only the issues addressed in the authorized representative’s decision will generally be entertained.

If the protest is timely elevated to the Commissioner, the authorized representative’s decision does not yet become final and demandable. The Supreme Court discussed this procedure in Light Rail Transit Authority v. CIR.

If the Commissioner denies the protest

File a petition for review with the CTA within 30 days from receipt of the Commissioner’s decision. A further motion for reconsideration filed with the Commissioner does not suspend or restart that 30-day CTA period under Revenue Regulations No. 18-2013.

If the BIR does not act within 180 days

The taxpayer generally has two mutually exclusive choices:

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

The Supreme Court confirmed these alternatives in Lascona Land Co., Inc. v. CIR. Once a taxpayer chooses to appeal the inaction, the taxpayer cannot later abandon that route and rely on the option of waiting for a decision.

The starting date for the 180-day period must be documented carefully. Preserve the protest’s filing receipt and, for reinvestigation, proof showing exactly when the complete supporting documents were submitted.

Appealing to the Court of Tax Appeals

An appeal is made by filing a petition for review with the CTA in Division. The petition must comply with the Revised Rules of the Court of Tax Appeals, the applicable Rules of Court, current filing directives, and docket-fee requirements.

The petition generally must:

Establish the CTA’s jurisdiction and timeliness;
State the complete material facts and issues;
Explain the grounds for reversing the BIR;
Be verified;
Contain the required certification against forum shopping;
Attach a legible duplicate original or certified true copy of the challenged decision, when applicable; and
Be accompanied by proof of payment of the required docket fees.

CTA litigation is evidence-intensive. Engage a Philippine tax lawyer well before the deadline so the petition, annexes, authorizations, filing method, and fees can be completed properly.

A CTA appeal does not automatically stop collection

Under Republic Act No. 9282, an appeal to the CTA generally does not suspend payment, levy, distraint, or sale of the taxpayer’s property. The CTA may suspend collection when it finds that collection may jeopardize the interests of the government or the taxpayer. It may require a deposit or a surety bond of not more than twice the amount claimed.

If you receive a warrant of distraint or levy, garnishment notice, final notice before seizure, collection suit, or another immediate collection measure, obtain legal assistance at once. A demand or collection document issued after a protest may, depending on its language and circumstances, be treated as a denial or final action that starts an appeal period.

Evidence to preserve

Keep a secure, complete assessment file containing:

Letter of Authority and all audit authorizations;
Document requests, summonses, and audit correspondence;
Notice of Discrepancy and response;
PAN, response, and proof of filing;
FLD/FAN, all schedules, and envelope or delivery records;
Written record of the actual receipt date and recipient;
Administrative protest and every annex;
Proof of filing with the correct BIR office;
Proof and inventory of the supporting documents submitted within 60 days;
Minutes, emails, and letters documenting meetings or discussions;
Tax returns and filing confirmations;
Books, ledgers, invoices, receipts, contracts, bank records, and reconciliations;
Waivers of the statute of limitations and related acceptance records;
FDDA or other denial, including proof of receipt;
Collection letters, warrants, and garnishment notices; and
Corporate resolutions, powers of attorney, and other representative-authority documents.

Preserve originals and readable electronic copies. Do not alter metadata or recreate missing records without clearly documenting what was reconstructed and from which source.

Common mistakes

Protesting only the PAN and failing to protest the FLD/FAN;
Counting from the wrong receipt date;
Filing a generic objection without issue-specific facts and law;
Failing to identify reconsideration or reinvestigation;
Requesting reinvestigation without specifying the additional evidence;
Missing the 60-day supporting-document deadline;
Filing with an examiner, RDO, or office other than the office of the FLD/FAN signatory;
Disputing only some findings unintentionally;
Assuming informal negotiations or settlement discussions stop the deadline;
Filing another motion with the Commissioner instead of a timely CTA petition;
Assuming a CTA appeal automatically suspends collection;
Losing the received copy, registry receipt, delivery proof, or annex inventory; and
Waiting until the last day to retain counsel.

When legal help is urgent

Seek a Philippine tax lawyer immediately if:

The 30-day protest or CTA deadline is near;
The amount is material to the taxpayer or business;
Several tax types or taxable years are involved;
The BIR alleges fraud, a false return, or deliberate tax evasion;
You dispute whether or when the notice was received;
A waiver, replacement audit authority, or reassignment of revenue officers is involved;
The FDDA or another denial has arrived;
You receive a final demand, warrant, garnishment, levy, or seizure notice;
The BIR has initiated civil or criminal proceedings; or
You believe the assessment was issued after the prescriptive period.

Frequently asked questions

Can I protest a PAN?

You may and ordinarily should respond to a PAN within 15 days, but a PAN response is not the statutory administrative protest against the FLD/FAN. If an FLD/FAN follows, file a separate valid protest within 30 days from its receipt.

Which is better: reconsideration or reinvestigation?

Use reconsideration when existing records are sufficient. Use reinvestigation when additional or newly discovered evidence is necessary. The correct choice depends on what is already in the audit record and what evidence is still needed.

Can the BIR extend the 30-day or 60-day period?

Do not rely on an extension. BIR rules and operational guidance treat these periods as mandatory and non-extendible.

Is an email protest enough?

Do not assume so. File through a method officially accepted by the office of the authorized representative who signed the FLD/FAN, and obtain reliable proof of timely filing and the complete attachments received.

What if I agree with only part of the assessment?

Identify and pay or otherwise address the undisputed portion, while clearly protesting each disputed issue. Amounts attributable to issues not properly disputed may become final and collectible.

What if the BIR does nothing for 180 days?

You may generally appeal the inaction to the CTA within the next 30 days or wait for the final BIR decision and appeal within 30 days from receipt. The choices are mutually exclusive, and the correct 180-day starting date must be verified.

Does a defective assessment mean I can ignore it?

No. Raise the defect through a timely protest and, if necessary, a timely CTA appeal. Whether a defect invalidates the assessment depends on the notice, audit record, governing rules, and controlling cases.

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

The assessment will generally be treated as final, executory, and demandable. Obtain urgent legal advice to examine service, receipt, jurisdictional defects, prescription, collection status, and any remedy that may remain. A late protest by itself normally does not revive the right to dispute the assessment.

Official legal sources

This article provides general legal information, not legal or tax advice for a specific assessment. Deadlines and remedies depend on the actual notices, receipt dates, audit record, and taxpayer circumstances. Sources were checked as of August 3, 2026.