Quick answer

If you disagree with a BIR deficiency-tax assessment, file a valid written administrative protest within 30 days from receipt of the Formal Letter of Demand and Final Assessment Notice (FLD/FAN). Address and file it with the BIR office and authorized official that issued the FLD/FAN. You may file personally or by registered mail; keep conclusive proof of filing.

Choose one remedy:

Request for reconsideration: asks the BIR to reevaluate the assessment using the records already submitted.
Request for reinvestigation: relies on newly discovered or additional evidence. Identify that evidence in the protest and submit all supporting documents within 60 days from filing the protest.

If the BIR denies the protest, the usual deadline to appeal to the Court of Tax Appeals (CTA) is 30 days from receipt of the decision. If the BIR does not act within the applicable 180-day period, you may either appeal the inaction to the CTA during the next 30 days or wait for a final BIR decision and appeal within 30 days after receiving it. Those choices are mutually exclusive.

These periods are mandatory and generally non-extendible. Missing one can make the assessment final, executory, and demandable. The governing rule is Section 228 of the National Internal Revenue Code, implemented principally by Revenue Regulations No. 18-2013.

First identify the document you received

Not every BIR notice is protested in the same way.

Document	What it means	Immediate response
Notice of Discrepancy (NOD)	Preliminary audit findings; not yet a deficiency assessment	Participate in the Discussion of Discrepancy and submit explanations and evidence promptly. Under the current process, this stage generally must not extend beyond 30 days from receipt.
Preliminary Assessment Notice (PAN)	Proposed assessment stating the factual and legal bases	If you disagree, respond within 15 days from receipt. A PAN response is useful but is not the formal Section 228 protest.
FLD/FAN	The formal assessment and demand for payment	File the written administrative protest within 30 days from receipt.
Final Decision on Disputed Assessment (FDDA)	Decision granting or denying the administrative protest, wholly or partly	Choose and perfect the proper administrative or CTA appeal within 30 days.
Collection letter, Final Notice Before Seizure, Warrant of Distraint or Levy, or Warrant of Garnishment	The BIR is treating the account as collectible	Obtain urgent tax counsel. The validity of the collection action and the correct appeal period depend on whether the underlying assessment or administrative appeal has become final.

The BIR’s official summary of the assessment process appears in RMC No. 15-2020 and its taxpayer guidelines.

The critical deadlines

Treat these as calendar-day deadlines and calculate them conservatively from documented receipt. Do not assume that a meeting, telephone call, follow-up letter, settlement discussion, or informal request will suspend a period.

Event	Period	Consequence of missing it
Receipt of PAN	15 days to respond	BIR may treat the taxpayer as in default and issue the FLD/FAN
Receipt of FLD/FAN	30 days to file a valid protest	Assessment generally becomes final, executory, and demandable
Filing a request for reinvestigation	60 days to submit all relevant supporting documents	Taxpayer may be barred from contesting the assessment through additional evidence
BIR action on a reconsideration	180 days counted from filing the protest	Inaction may be appealed to the CTA during the next 30 days, or the taxpayer may await a final decision
BIR action on a reinvestigation	180 days counted from submission of the required documents within the 60-day period	Same alternatives apply
Receipt of an adverse FDDA or CIR decision	30 days for the proper appeal	Decision and assessment may become final
Filing an administrative or CTA appeal from an FDDA	5 days to furnish the required BIR office a copy	Possible procedural and administrative consequences

The 180-day period for reconsideration and reinvestigation does not necessarily begin on the same date. RR No. 18-2013 counts it from filing for reconsideration, but from timely submission of the required documents for reinvestigation.

How to prepare the protest

1. Preserve proof of receipt immediately

Keep the entire set of documents exactly as received, including:

The FLD, every FAN and Details of Discrepancies;
The envelope, registry notice, tracking record, transmittal sheet, and return card;
The name, position, and authority of the person who accepted the documents;
Reception-desk logs, security logs, email notifications, and CCTV footage, if relevant;
The PAN, NOD, Letter of Authority, audit correspondence, and earlier submissions; and
A written chronology of every receipt, meeting, filing, and telephone call.

Service may be personal, by mail, or—under prescribed conditions—by substituted service. A notice left with a clerk, a person in charge of a business address, or a competent adult at a residence may qualify in appropriate circumstances. Refusing delivery does not necessarily prevent valid service. The procedures are detailed in RMO No. 40-2019.

If receipt is disputed, do not simply ignore the assessment. File a protective response within the earliest reasonably arguable deadline while expressly reserving the objection to invalid service.

2. Reconcile every assessed item

Create a schedule for each tax type and taxable period showing:

Amount assessed by the BIR;
Amount, if any, admitted by the taxpayer;
Amount disputed;
BIR adjustment or discrepancy;
Taxpayer’s factual explanation;
Documentary support; and
Legal basis.

An FLD/FAN can contain several independent findings. If the protest disputes only some findings—or gives no facts and legal basis for others—the unchallenged items may become final and collectible. Pay any genuinely undisputed portion through the BIR-prescribed process and preserve the payment record.

3. Choose reconsideration or reinvestigation carefully

A reconsideration is appropriate when the necessary evidence is already in the BIR record and the dispute concerns the interpretation of existing documents, facts, or law. The special 60-day document-submission period does not apply.

A reinvestigation is appropriate when the case requires new or additional evidence. The protest must identify the evidence to be presented, and all relevant supporting documents must be submitted within 60 days. BIR rules state that evaluation will be based on documents submitted within that period. A reinvestigation that the Commissioner grants can also affect the prescriptive period for collection.

The remedies are alternatives. Filing one generally precludes changing to the other. Under RMO No. 26-2016, a protest that does not clearly request reinvestigation is treated as a request for reconsideration.

4. Include the required content

At minimum, the protest should:

Identify the taxpayer, TIN, address, assessment numbers, tax types, periods, and amounts;
State the date the FLD/FAN was received;
Clearly label the filing as a request for reconsideration or request for reinvestigation;
If reinvestigation is requested, specify the newly discovered or additional evidence;
Identify every disputed finding and amount;
State the material facts supporting the objection to each finding;
Cite the applicable statutes, regulations, and jurisprudence for each ground;
Explain the requested correction or cancellation;
Identify and index all attachments;
Reserve applicable objections to authority, prescription, due process, service, computation, penalties, and interest; and
Be signed by the taxpayer or a duly authorized representative, with the required proof of authority.

A generic letter saying only that the taxpayer “disagrees” or requests “reconsideration” is dangerous. RR No. 18-2013 provides that a protest lacking the prescribed information may be treated as void and without effect.

5. File with the correct BIR office

Address the protest to the Regional Director, Assistant Commissioner, or other authorized higher revenue official that issued the FLD/FAN, and file it with that official’s office.

The recognized filing methods in the BIR’s published guidelines are:

Personal filing: obtain a receiving copy bearing the date, time, office, and receiving officer’s name and signature; or
Registered mail: retain the registry receipt, postmarked envelope records, tracking history, and complete duplicate of the submission. The post-office stamp is treated as the filing date under the BIR guideline.

Do not rely solely on ordinary mail, courier delivery, email, or an upload unless the issuing office confirms in writing that the method is officially authorized for that filing.

6. Submit reinvestigation evidence within 60 days

Organize the submission so the BIR can trace each document to a disputed issue. Common supporting evidence includes:

Filed returns and proof of payment;
Audited financial statements, trial balances, general and subsidiary ledgers;
Invoices, credit or debit notes, withholding certificates, and official payment records;
Contracts, purchase orders, delivery records, import documents, and bank statements;
Payroll and employee-benefit records;
Reconciliations between returns, books, financial statements, and third-party data;
Board resolutions, special powers of attorney, and proof of signatory authority;
Sworn statements where firsthand facts genuinely require them; and
Copies of all documents previously submitted during the audit.

Submit a signed cover letter and indexed document list. Keep originals intact and preserve native electronic records and metadata. Do not assume that documents offered after the 60-day period will be accepted.

Grounds that should be checked

The correct grounds depend on the audit record. Common issues worth examining include the following.

Lack of authority to conduct the audit

Determine whether the audit required a valid Letter of Authority, whether the correct taxable period and taxes were covered, and whether the revenue officers who actually conducted the examination were properly authorized.

The Supreme Court has held that an assessment resulting from an audit conducted without the required authority may be void. It has also ruled that replacing the officers named in an LOA without a new or properly issued authority can violate due process. See Medicard Philippines, Inc. v. CIR and CIR v. McDonald’s Philippines Realty Corp.. Whether an LOA was legally required still depends on the kind of liability and how it arose.

Prescription

The general rule is that the BIR must assess an internal revenue tax within three years after the statutory filing deadline, or from actual filing if the return was filed late. Important exceptions include:

A false or fraudulent return with intent to evade tax;
Failure to file a return;
A valid written agreement extending the assessment period;
Statutory events suspending the period; and
Special rules applicable to particular taxes or proceedings.

For a false or fraudulent return with intent to evade tax, or no return, Section 222 generally allows assessment within 10 years after discovery. Prescription analysis is document- and date-sensitive; review the original returns, amended returns, waivers, dates of execution and acceptance, and proof of issuance and service.

Failure to issue or properly serve a PAN

A PAN is ordinarily required. Section 228 allows an immediate FLD/FAN only in five situations:

A mathematical error appearing on the face of the return;
A discrepancy between tax withheld and tax actually remitted;
Carryover of the same excess creditable withholding tax for which a refund or tax credit was claimed;
Unpaid excise tax on excisable articles; or
Transfer to a non-exempt person of an article acquired by an exempt person.

Outside an exception, the taxpayer must be given the prescribed opportunity to answer the PAN. Issuing the FLD/FAN before the 15-day response period expires can violate due process. See CIR v. Metro Star Superama, Inc..

Failure to state the factual and legal bases

The PAN and FLD/FAN must tell the taxpayer in writing the facts and law supporting the assessment. Merely listing tax types, amounts, or conclusions may be insufficient if the taxpayer cannot intelligently determine why the BIR assessed the tax.

An FDDA must likewise state its factual and legal bases and identify itself as the final decision. The legal effect of a defect in an FDDA may differ from the effect of a void FLD/FAN, so challenge each document separately rather than assuming that one defect automatically cancels everything.

Invalid or unproven service

When a taxpayer specifically denies receipt, proof that the BIR merely prepared or mailed a notice may not always establish valid receipt. Examine registry records, return cards, signatures, authority of the recipient, address used, and compliance with substituted-service requirements.

Failure to consider the taxpayer’s evidence

The opportunity to respond must be meaningful. Identify evidence and explanations the BIR overlooked, explain their effect on the computation, and connect them to each disputed finding. Do not rely only on the assertion that the BIR “ignored” the protest; show precisely what was submitted, when, and why it changes the result.

Errors on the merits

Test the BIR’s computation against the governing law for the taxable period. Common disputes involve:

Recognition and timing of income or sales;
Deductibility and substantiation of expenses;
VAT output and input-tax treatment;
Withholding-tax classification and timing;
Tax-treaty or statutory exemptions;
Attribution of third-party information;
Duplicate assessments or payments;
Surcharges and interest; and
Application of payments, credits, or prior adjustments.

Tax rates and documentation rules can change between taxable periods. Use the law applicable to the year under audit, not automatically the current rule.

What happens after the protest

If an authorized BIR representative issues an adverse FDDA

Within 30 days from receipt, the taxpayer may generally choose either:

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

An administrative appeal to the Commissioner is limited to reconsideration; reinvestigation is no longer available after the FDDA. Only issues covered by the authorized representative’s decision will be entertained.

If the Commissioner later denies the administrative appeal, file the CTA petition within 30 days from receipt. A further motion for reconsideration of the Commissioner’s own denial does not toll that CTA deadline.

If the BIR does not act within 180 days

The taxpayer has two mutually exclusive choices:

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

The Supreme Court confirmed this choice in Lascona Land Co., Inc. v. CIR. Once the taxpayer appeals the inaction, the taxpayer cannot later use the alternative of awaiting and separately appealing the eventual decision.

Before selecting either route, assess the strength of the existing administrative record, continuing interest exposure, possible collection action, and the risk of miscalculating the 180-day starting point.

If appealing to the CTA

A CTA appeal is a judicial case, not another BIR letter. It requires a verified petition for review, a certification against forum shopping, the relevant decision and records, proof of service, and payment of docket and other lawful fees. Current paper and electronic-submission requirements must also be followed. The governing procedures appear in the Revised Rules of the Court of Tax Appeals.

Within five days after filing an appeal from an FDDA with the Commissioner or CTA, furnish a copy to:

The Chief of the Assessment Division for regional cases; or
The concerned Head Revenue Executive Assistant for Large Taxpayers Service or National Investigation Division cases.

This requirement is stated in RMC No. 43-2023.

Does a protest stop collection?

A timely and valid administrative protest generally prevents the disputed assessment from becoming final while the proper administrative proceeding remains pending. The BIR should not use summary collection remedies for a deficiency assessment that has not become final and executory.

A CTA appeal, however, does not automatically suspend collection. Under Section 11 of Republic Act No. 9282, the CTA may suspend collection when collection could jeopardize the government’s or taxpayer’s interests. The taxpayer must request that relief and support it with affidavits and documentary evidence. The CTA may require a deposit or surety bond of no more than twice the amount claimed.

In CIR v. CTA and American Wire & Cable Co., Inc., the Supreme Court sustained CTA relief where the BIR pursued collection before the taxpayer’s 30-day judicial appeal period had expired and the assessment had not become final.

Interest may continue to affect the exposure while the dispute is unresolved. The general Section 249 rate has been 12% under RR No. 21-2018. Prospectively, qualifying micro and small taxpayers receive a 50% reduced rate—currently 6%—under RR No. 6-2024. Classification is based on gross business sales: below ₱3 million for micro taxpayers and ₱3 million to below ₱20 million for small taxpayers, subject to the detailed rules in RR No. 8-2024.

Common mistakes

Treating a PAN response as the required protest to the FLD/FAN;
Counting from the date printed on the notice instead of preserving and analyzing the date of receipt;
Filing a bare request without facts and legal grounds for every disputed item;
Failing to specify reconsideration or reinvestigation;
Calling the protest a reinvestigation but not identifying and submitting additional evidence within 60 days;
Sending the protest to the revenue officer instead of filing it with the office of the authorized official who issued the FLD/FAN;
Relying on ordinary mail, courier tracking, email, or verbal assurances without official proof of filing;
Ignoring undisputed findings;
Waiting for a collection notice after receiving an adverse FDDA;
Filing another motion with the Commissioner after the Commissioner’s own denial and assuming that it suspends the CTA deadline;
Appealing inaction without correctly identifying when the 180-day period began; and
Assuming that a CTA petition automatically stops levy, garnishment, or distraint.

When professional help is urgent

Consult a Philippine tax lawyer immediately if:

Fewer than 10 days remain before a protest or CTA deadline;
You received an FDDA, CIR denial, warrant of distraint or levy, garnishment order, seizure notice, or collection complaint;
The BIR is contacting banks, customers, tenants, or government payors;
Receipt or service of the PAN, FLD/FAN, or FDDA is disputed;
The assessment alleges fraud, substantial underdeclaration, or willful failure to file or remit tax;
The audit was conducted by officers who may not have been authorized;
Waivers of the statute of limitations were signed;
Several tax types or taxable years are involved;
Essential records are missing or held by another person; or
Payment or collection would threaten payroll, banking facilities, property, or continuing operations.

A tax lawyer should direct the legal grounds and protect the appeal periods. A CPA or accounting team should produce the reconciliations and documentary trail. Their work should be coordinated so the protest’s legal theory matches the accounting evidence.

Frequently asked questions

Must I pay the assessment before protesting it?

Generally, no payment is required merely to file a timely administrative protest to the disputed portion of an FLD/FAN. Any undisputed portion should be paid. Payment, compromise, abatement, and refund strategies have separate legal consequences and should be evaluated before funds are remitted.

Can I ask the BIR for more than 30 or 60 days?

Do not rely on an extension. The BIR treats the periods under RR No. 18-2013 as mandatory and non-extendible.

What if I replied to the PAN but did not protest the FLD/FAN?

A PAN reply does not replace the Section 228 protest. Unless a valid protest was filed within 30 days from receipt of the FLD/FAN—or the assessment itself is void for a legally sustainable reason—the BIR may treat the assessment as final.

What if the BIR never issued a PAN?

Check whether one of Section 228’s five exceptions applies. If none does, timely raise the omission as a due-process ground. Do not ignore the FLD/FAN merely because you believe the PAN was missing.

What if I never received the FLD/FAN?

Preserve evidence concerning your registered and known addresses, authorized recipients, mail handling, and the first document you actually received. Respond promptly to any collection notice and expressly contest service. Whether an assessment was validly served is an evidentiary question.

Can I wait indefinitely after the 180-day period?

You may choose to wait for a final decision instead of appealing the inaction, but monitor all communications and collection activity. Once a final decision arrives, the 30-day CTA period begins. Obtain advice before choosing because an appeal of inaction and waiting for the decision are mutually exclusive remedies.

Can the BIR collect while my CTA case is pending?

A CTA appeal alone does not automatically suspend collection. File a supported motion to suspend collection when necessary and be prepared for a possible deposit or bond requirement.

Can I settle instead of litigating?

The Tax Code allows compromise in specified circumstances, including reasonable doubt about the claim’s validity or demonstrated financial incapacity, subject to statutory minimums and approval requirements. A settlement request does not safely replace a protest or suspend an appeal deadline unless a controlling written action legally produces that effect.

Official sources

This article provides general legal information, not legal or tax advice. The correct remedy depends on the notices, proof of service, audit record, taxable period, and authority of the issuing officials. Sources and procedures were checked as of 10 August 2026.