Quick answer

If you receive a Formal Letter of Demand and Final Assessment Notice (FLD/FAN) from the Bureau of Internal Revenue (BIR), you generally have 30 days from receipt to file a valid written administrative protest. Your protest must be either a request for reconsideration or a request for reinvestigation. If you choose reinvestigation, you must submit the relevant supporting documents within 60 days from filing the protest. A request for reconsideration is decided on the existing record, so the separate 60-day document-submission period does not apply.

Do not confuse an FLD/FAN with a Preliminary Assessment Notice (PAN). A PAN is normally answered within 15 days from receipt. It is the FLD/FAN—not the PAN—that is administratively protested under Section 228 of the National Internal Revenue Code (NIRC).

The main deadlines are:

Stage	General deadline
Reply to PAN	15 days from receipt
Protest against FLD/FAN	30 days from receipt
Supporting documents for reinvestigation	60 days from filing the protest
BIR action period	Generally 180 days, computed under the applicable rule
CTA appeal from an adverse final decision	30 days from receipt
CTA appeal based on BIR inaction	30 days after expiration of the applicable 180-day period, if you choose the inaction remedy

Missing one of these deadlines can cause all or part of the assessment to become final, executory, and demandable.

First identify exactly what BIR document you received

The correct response depends on the document.

If it is a Preliminary Assessment Notice

A PAN contains the BIR's proposed assessment. Under Revenue Regulations (RR) No. 18-2013, the taxpayer generally has 15 days from receipt to respond. The PAN should show in detail the facts and the law, rules, regulations, or jurisprudence supporting the proposed deficiency.

The PAN stage is important because it gives you an early opportunity to correct factual errors, explain transactions, submit reconciliations, and challenge the BIR's legal position. But the Supreme Court has clarified that the statutory administrative protest contemplated by Section 228 is directed against the FLD/FAN, not against the PAN. (eLibrary)

A PAN is not always required. Section 228 and RR No. 18-2013 allow the BIR to issue an FLD/FAN outright in specified situations, including certain mathematical errors appearing on the face of a return, discrepancies between withholding and amounts actually remitted, specified excess-credit carryover situations, unpaid excise taxes, and transfers of exempt articles to non-exempt persons.

If it is an FLD/FAN

This is the critical document for purposes of a Section 228 protest.

The taxpayer or an authorized representative or tax agent may file a written protest against the FLD/FAN within 30 days from receipt. Failure to file a valid protest within that period generally makes the assessment final, executory, and demandable.

If it is an FDDA or another decision denying your protest

A Final Decision on Disputed Assessment (FDDA) should state the factual and legal grounds for the decision and indicate that it is the final decision of the Commissioner or the Commissioner's duly authorized representative.

Do not simply file another letter with the same BIR office without first determining who issued the decision and what remedy remains. A 30-day CTA deadline may already be running.

If you first learn about the assessment through a collection letter, warrant, levy, or garnishment

Treat the matter as urgent. There may be an issue concerning whether the FLD/FAN was validly served or whether an assessment became final before collection began. The Supreme Court continues to emphasize that, in the ordinary course, a valid assessment and administrative due process are prerequisites to enforcing collection of a deficiency tax. (Lawphil)

Step 1: Establish the exact date of receipt

Do not calculate a protest deadline merely from the date printed on the assessment.

The important date is normally the legally relevant date of receipt or completion of service. Preserve the envelope, registry notice, courier tracking record, receiving copy, email if officially authorized, and any internal company receiving log.

BIR rules allow assessment notices to be served personally and, when appropriate, through substituted service or mail. For example, RMO No. 40-2019 provides rules for personal service, substituted service, registered mail, professional courier, and ordinary mail. It also states that service upon a duly appointed tax agent or practitioner is deemed service upon the taxpayer.

For registered mail, RMO No. 40-2019 states that service is complete upon actual receipt or after five days from receipt of the postmaster's first notice, whichever is earlier; ordinary-mail service is considered complete after 10 days from mailing. These rules can make a disputed service date legally significant.

Step 2: Choose reconsideration or reinvestigation carefully

RR No. 18-2013 recognizes two forms of protest.

A request for reconsideration asks the BIR to reevaluate the assessment using the records already available. It may raise questions of fact, law, or both. No new evidence is required.

A request for reinvestigation asks the BIR to reevaluate the assessment using newly discovered or additional evidence that the taxpayer intends to present. It may likewise involve factual or legal questions.

The distinction has consequences.

For a reinvestigation, all relevant supporting documents must be submitted within 60 days from filing the protest. The regulation expressly says that this 60-day rule does not apply to requests for reconsideration. The Supreme Court confirmed this interpretation in Commissioner of Internal Revenue v. Maxicare Healthcare Corporation.

There can also be a prescription consequence. Section 223 of the NIRC provides for suspension of the relevant prescriptive period when a taxpayer requests a reinvestigation that is granted by the Commissioner. The Supreme Court has distinguished this from a reconsideration, which does not produce the same statutory effect. (eLibrary)

Accordingly, do not call a protest a "reinvestigation" merely because it sounds broader. Choose the remedy that corresponds to what you actually need to prove.

Step 3: Make the protest valid, not merely timely

A letter saying "we disagree with the assessment" is dangerous.

RR No. 18-2013 requires the protest to state:

whether it is a request for reconsideration or reinvestigation;
if reinvestigation is requested, the newly discovered or additional evidence intended to be presented;
the date of the assessment notice; and
the applicable law, rules, regulations, or jurisprudence supporting the protest.

The protest should also clearly identify the taxpayer, TIN, assessment number, taxable period, tax type, amounts being contested, relevant facts, computations, and the relief requested.

Address every material assessment issue separately. RR No. 18-2013 provides that if an FLD/FAN contains several issues and the taxpayer disputes only some of them, the assessment attributable to the undisputed issues becomes final, executory, and demandable. The same problem can arise if an issue is nominally disputed but the protest fails to state its factual and legal basis.

Step 4: File the written protest within 30 days and prove that you filed it

The controlling regulation requires a written protest against the FLD/FAN within 30 days from receipt.

Follow the filing instructions of the BIR office handling or issuing the assessment. Obtain reliable proof showing exactly what was submitted and when it was received. If filing physically, keep a complete stamped receiving copy. If a particular BIR issuance or written instruction authorizes another transmission method for your case, preserve its acknowledgement and transmission records.

Do not assume that sending an ordinary email, uploading documents to a general BIR electronic service, or handing papers informally to a revenue officer automatically constitutes a valid Section 228 protest.

Step 5: If you chose reinvestigation, complete the evidence within 60 days

For a request for reinvestigation, the taxpayer must submit all relevant supporting documents within 60 days from filing the protest. RR No. 18-2013 defines relevant supporting documents as those necessary to support the legal and factual bases of the taxpayer's dispute, as determined by the taxpayer.

This means the taxpayer should not wait for the BIR to identify every document it might need.

Depending on the assessment, useful evidence may include tax returns, audited financial statements, general ledgers, subsidiary ledgers, invoices, official receipts or other invoicing records applicable to the period, withholding certificates, bank records, contracts, import documents, schedules reconciling tax returns to accounting records, proof of tax payments, correspondence with the BIR, and records supporting exemptions, deductions, input taxes, tax credits, or withholding.

Submit an organized transmittal identifying each document and the assessment issue it supports. Retain proof of receipt of both the documents and the transmittal.

Step 6: Examine whether the assessment itself is legally defective

A protest should challenge not only the BIR's arithmetic but also the validity of the assessment process where the facts support such a challenge.

Lack of factual or legal basis

Section 228 requires the taxpayer to be informed in writing of the law and facts on which the assessment is based; otherwise, the assessment is void. RR No. 18-2013 imposes the same requirement on an FLD/FAN. (eLibrary)

A bare tax computation is not necessarily enough. The taxpayer must receive enough information to understand why the tax is allegedly due and to prepare an intelligent protest.

The Supreme Court reiterated in 2026 that a taxpayer must be given the factual and legal basis necessary to respond effectively to a claimed tax liability and that the BIR ordinarily cannot bypass a valid assessment before pursuing collection. (Lawphil)

Defective demand for payment

A valid final assessment ordinarily must embody an actual demand for payment. Supreme Court jurisprudence has also required a sufficiently definite assessment, including the amount demanded and a definite due date for payment. (eLibrary)

Failure to issue a required PAN

If the case does not fall within one of Section 228's express exceptions, failure to comply with the required PAN process may present a due-process issue.

Defective service

Since the protest period runs from receipt, whether and when the PAN, FLD/FAN, or FDDA was properly served may itself become disputed. Preserve every piece of evidence concerning delivery and identify who actually received the document. BIR rules expressly regulate personal, substituted, and mail service.

Prescription

As a general rule, Section 203 requires internal revenue taxes to be assessed within three years from the last day prescribed for filing the return or, if the return was filed late, from actual filing. There are important exceptions, including the rules applicable to false or fraudulent returns with intent to evade tax, failure to file a return, and valid written extensions of the assessment period. (eLibrary)

Prescription is highly dependent on dates, the type and timing of the return, waivers, the issuance and release of the assessment, allegations of fraud, and possible statutory suspensions. It should therefore be examined from the complete audit record rather than assumed from the age of the taxable year alone.

Step 7: Calendar the 180-day period

The 180-day rule is another frequent source of lost remedies.

Under RR No. 18-2013, for a request for reconsideration, the 180-day period is counted from the filing of the protest. For a request for reinvestigation, it is counted from the taxpayer's submission of the required supporting documents within the 60-day document period.

Keep a written deadline calendar showing:

receipt of the FLD/FAN;
30-day protest deadline;
date the protest was actually filed;
if applicable, the 60-day supporting-document deadline;
actual date supporting documents were submitted;
end of the applicable 180-day period; and
every later date on which a BIR decision or FDDA was received.

These dates may determine CTA jurisdiction.

What happens if the BIR denies the protest?

The answer depends partly on who issued the denial.

If the protest is denied in whole or in part by a duly authorized representative of the Commissioner, RR No. 18-2013 allows the taxpayer, within 30 days from receipt, either to:

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

No request for reinvestigation is allowed at that administrative-appeal stage, and the regulation limits the matters entertained by the Commissioner to issues raised in the authorized representative's decision.

If the Commissioner denies the protest or administrative appeal, the taxpayer generally has 30 days from receipt to appeal to the CTA. Importantly, RR No. 18-2013 expressly provides that filing a motion for reconsideration of the Commissioner's denial does not suspend the 30-day CTA appeal period.

What if the BIR does nothing for 180 days?

The Supreme Court recognizes two choices when the BIR fails to act within the statutory period.

The taxpayer may:

treat the inaction as a denial and 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, even beyond 180 days, and then appeal that decision to the CTA within 30 days after receipt. (eLibrary)

These remedies are mutually exclusive. Once the taxpayer chooses to appeal the inaction, the taxpayer cannot simultaneously continue waiting for a later administrative decision as though no judicial appeal had been taken.

Do not automatically assume that the assessment becomes final merely because the taxpayer did not appeal immediately after the 180th day. The Supreme Court's Lascona Land line of cases recognizes the taxpayer's option to await a final decision. (eLibrary)

Appealing to the Court of Tax Appeals

A disputed BIR assessment is ordinarily elevated to a CTA Division through a Petition for Review.

The Revised Rules of the Court of Tax Appeals provide a 30-day period for an adversely affected taxpayer to appeal a decision or qualifying inaction of the Commissioner. The Supreme Court and CTA have repeatedly treated the applicable appeal period as jurisdictional, so a taxpayer should never plan around the possibility of obtaining extra time. (Court of Appeals)

A CTA case is litigation, not simply another BIR protest. The petition must comply with the CTA Rules and applicable Rules of Court, and the taxpayer must be prepared to prove both the procedural defects asserted and the substantive correctness of its tax position.

Does filing a CTA case stop BIR collection?

Not automatically.

Section 11 of the CTA law and the CTA Rules provide that an appeal does not by itself suspend payment, levy, distraint, or sale for satisfaction of the tax liability. The CTA may, however, suspend collection when the statutory standards are met. The court may require a deposit or a surety bond subject to the governing law and jurisprudence. (eLibrary)

If an FDDA is followed by a warrant of distraint and levy, garnishment, seizure notice, or another active collection measure, legal assistance should be obtained immediately because a separate application for suspension of collection may need to be considered.

Evidence you should preserve

Keep the complete tax-audit file, not merely the protest letter. In particular, preserve:

the Letter of Authority and any amendments or replacements;
notices of discrepancy and audit correspondence;
PAN and all attachments;
your PAN reply and proof of filing;
FLD/FAN and all assessment schedules;
the original envelopes, registry notices, courier records, receiving logs, and proof of delivery;
the protest and stamped or otherwise verifiable proof of BIR receipt;
every supporting document submitted during reinvestigation and its transmittal;
accounting records and reconciliations underlying the disputed items;
tax returns and proof of payment;
relevant contracts, invoices, withholding certificates, bank records, and third-party documents;
all BIR letters after the protest;
FDDA or other denial and proof of its receipt; and
any collection letter, warrant, levy, or garnishment document.

Dates and proof of service can be just as important as the tax computations themselves.

Common mistakes that can make an otherwise good case fail

One of the most serious mistakes is protesting the wrong document. Responding to a PAN does not replace the separate 30-day protest required after receipt of the FLD/FAN. (eLibrary)

Another is filing a generic protest that does not identify whether reconsideration or reinvestigation is requested or does not give the factual and legal basis for each disputed assessment issue. Under RR No. 18-2013, that can cause the protest—or particular issues—to lose legal effect.

Other dangerous mistakes include missing the 60-day evidence deadline after choosing reinvestigation, relying on an unproven filing date, ignoring an issue because the amount is small, miscalculating the 180-day period, waiting more than 30 days after an adverse final decision, and filing another motion with the Commissioner while assuming it has stopped the CTA deadline.

Also avoid assuming that substantive defenses can cure a jurisdictional deadline. A strong tax argument may never be reached if the assessment has already become final because the required protest or appeal was filed late.

When legal help is urgent

Immediate tax-law assistance is particularly important when the 30-day protest or CTA deadline is already running; the 60-day reinvestigation period is about to expire; an FDDA has been received; the BIR has issued a collection letter, warrant of distraint and levy, garnishment, or seizure notice; the BIR alleges fraud or a false return; the amount is substantial; there is a dispute over whether the assessment was properly served; or the assessment may already be prescribed.

Early review is especially valuable because some defenses depend on procedural facts that are easy to lose—such as the envelope showing mailing information, the identity of the person who received the notice, or the receiving stamp on a protest.

FAQ

Can I protest a PAN?

You should normally respond to a PAN within 15 days, but the formal Section 228 administrative protest is directed against the subsequent FLD/FAN.

Do I have to pay the assessment before I can protest it?

A taxpayer is not generally required to prepay the disputed amount merely to file the administrative protest contemplated by Section 228. However, any assessment issue that is not properly disputed can become final and demandable, and collection issues become more significant after a final adverse decision.

Which is better: reconsideration or reinvestigation?

Neither is universally better. Use reconsideration when the existing record is sufficient and the dispute concerns the BIR's interpretation, computation, or evaluation of existing evidence. Use reinvestigation when additional or newly discovered evidence is genuinely needed. Reinvestigation carries the 60-day document deadline and can also have different prescription consequences.

What happens if I miss the 30-day protest deadline?

RR No. 18-2013 provides that an FLD/FAN that is not validly protested within 30 days becomes final, executory, and demandable, and no reconsideration or reinvestigation will ordinarily be granted against an assessment that has already reached that status.

Can I submit my reinvestigation documents after 60 days?

The regulation requires all relevant supporting documents for a reinvestigation to be submitted within 60 days from filing the protest. Missing that period can have serious finality consequences. Do not rely on an informal assurance that late documents will be accepted.

If the BIR does not decide within 180 days, must I immediately go to the CTA?

No. Supreme Court jurisprudence allows you either to appeal the inaction within the prescribed 30-day period after the 180 days expire or to await the BIR's final decision and appeal that decision within 30 days after receipt. The two options are mutually exclusive. (eLibrary)

Can I file another motion for reconsideration after the Commissioner denies my administrative appeal?

You should not rely on such a motion to preserve your judicial remedy. RR No. 18-2013 expressly states that a motion for reconsideration of the Commissioner's denial does not toll the 30-day period for appeal to the CTA.

Is an assessment automatically valid because it came from the BIR?

No. Section 228 expressly requires the assessment to disclose its factual and legal bases, and Supreme Court jurisprudence requires compliance with the due-process rules governing valid assessments. Whether a particular defect actually invalidates an assessment depends on the documents and circumstances of the case.

Official sources

General-information disclaimer

This article provides general Philippine legal information and is not a substitute for legal or tax advice based on the complete assessment record. Tax protests are highly deadline-sensitive, and the correct remedy may depend on the precise document issued, who issued it, how and when it was served, the type of protest chosen, the evidence submitted, prior waivers or agreements, and later BIR action. Sources and procedures checked as of August 25, 2026.