Quick answer

To contest a Bureau of Internal Revenue deficiency assessment, file a valid written protest against the Formal Letter of Demand and Final Assessment Notice (FLD/FAN) within 30 days from receipt. Address and file it with the BIR official who signed the FLD/FAN, identify it expressly as either a request for reconsideration or a request for reinvestigation, and dispute every contested finding with specific facts and legal grounds.

If you choose reinvestigation, submit all relevant supporting documents within 60 days from filing the protest. Missing the 30-day protest deadline—or the 60-day document deadline for reinvestigation—can make the assessment final, executory, and demandable.

A reply to the Preliminary Assessment Notice (PAN) is not a substitute for the protest against the FLD/FAN.

Act immediately upon receipt

Keep the entire notice, including schedules and attachments, and record:

The exact date, time, address, and method of delivery
Who received and signed for it
The assessment numbers, taxes, taxable periods, and amounts
The issuing office and signatory
The date stated on the notice
Any payment or response deadline printed on it

Preserve the envelope, registry notice, courier tracking, receiving log, email trail, and any CCTV or witness evidence relevant to delivery. The date of receipt normally starts the protest period, and disputes over service are highly fact-dependent.

Treat the periods as calendar-day deadlines and file early. Do not assume that discussions with a revenue officer, a request for records, a pending meeting, or an informal assurance will extend them. Check promptly for any BIR issuance specifically extending deadlines because of a government work suspension or emergency.

Know which document you received

Notice of Discrepancy or audit discussion

A Notice of Discrepancy or an audit conference generally occurs before a formal assessment. Responding can resolve factual errors early, but it does not replace the remedies required after a PAN or FLD/FAN is issued.

Preliminary Assessment Notice

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

Use the PAN stage to submit an issue-by-issue explanation, correct computations, and provide documents already available. The BIR must ordinarily allow the 15-day response period before issuing the FLD/FAN. The Supreme Court has invalidated assessments where the BIR disregarded that opportunity, including in CIR v. Yumex Philippines Corporation and CIR v. Prime Steel Mill, Inc..

A PAN is not required in these statutory situations:

A mathematical error appears on the face of the return.
The tax withheld differs from the amount actually remitted by the withholding agent.
Excess creditable withholding tax claimed for refund or tax credit was also carried over and applied to the succeeding year.
Excise tax due on excisable articles was

Quick answer

To dispute a Bureau of Internal Revenue deficiency assessment, file a valid written protest against the Formal Letter of Demand and Final Assessment Notice (FLD/FAN) within 30 days from receipt. File it with the BIR official who signed the assessment, through the appropriate receiving office.

The protest must:

Identify whether it is a request for reconsideration or a request for reinvestigation.
State the assessment date and your date of receipt.
Address every disputed tax, period, finding, and amount.
State the supporting facts and applicable law, regulations, or jurisprudence.
Identify any additional evidence you intend to submit if requesting reinvestigation.
Be signed by the taxpayer or a properly authorized representative.
Be filed with reliable proof of the filing date.

A request for reinvestigation requires all relevant supporting documents to be submitted within 60 days from filing the protest. Missing the 30-day protest deadline—or, for reinvestigation, the 60-day document deadline—can make the assessment final, executory, and demandable.

Do not confuse a response to a Preliminary Assessment Notice (PAN) with the required protest against the FLD/FAN. Even if you answered the PAN, you must separately protest the FLD/FAN on time.

These deadlines come principally from Section 228 of the National Internal Revenue Code and Revenue Regulations No. 18-2013.

Identify the document you received

The correct response depends on the document’s legal stage.

Notice of Discrepancy or audit communication

A Notice of Discrepancy, discussion sheet, audit report, or similar communication usually precedes a formal assessment. Respond within the period written in the notice and provide documents strategically, but do not assume that this response will preserve your right to contest a later FLD/FAN.

Preliminary Assessment Notice

A PAN states the BIR’s proposed findings. The general rule is that the taxpayer has 15 days from receipt to respond.

A detailed PAN response may correct errors before a final assessment is issued. It should address the computations, facts, and legal grounds and attach documents already available. However, a PAN response is not the administrative protest required by Section 228.

The BIR may issue an FLD/FAN without first issuing a PAN only in the statutory exceptions:

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

Outside these exceptions, failure to give the taxpayer the required PAN and opportunity to respond may invalidate the assessment. The Supreme Court has treated receipt of the PAN as part of due process, including in Commissioner of Internal Revenue v. Metro Star Superama, Inc.. The BIR must also respect the 15-day response period before issuing the FLD/FAN, as explained in Commissioner of Internal Revenue v. Yumex Philippines Corporation.

Formal Letter of Demand and Final Assessment Notice

The FLD/FAN is the assessment that must generally be protested within 30 days from receipt. It should state the facts and the law, regulations, or jurisprudence supporting the assessment. It should also contain or be accompanied by the assessment details and amounts demanded.

Do not rely only on the document’s title. If a letter fixes a liability, demands payment, or states that it is the BIR’s final action, obtain tax counsel immediately to determine what deadline it triggers.

Final Decision on Disputed Assessment

An FDDA is the BIR’s ruling on a timely protest. It must state the material facts and legal bases for the decision and indicate that it is final. A conclusory decision that merely repeats amounts without addressing the protest may be defective, although that issue normally must be raised through a timely appeal. The Supreme Court discussed these requirements in Commissioner of Internal Revenue v. Liquigaz Philippines Corporation.

Record the date and manner of receipt

Most deadlines begin upon receipt, so preserve evidence of exactly when and how every notice arrived.

Keep:

The original envelope and registry or courier labels.
The complete notice, including schedules and attachments.
A scan or photograph showing the date stamp.
The registry notice, acknowledgment receipt, courier tracking, and delivery history.
The name and position of the person who accepted the document.
Records showing when the notice reached the taxpayer’s responsible officers.
Evidence of the taxpayer’s registered address at the relevant time.
Any power of attorney or appointment of a tax agent.

BIR notices may be served personally, by substituted service, or by mail or professional courier under RR No. 18-2013. Service on an appointed tax agent in circumstances covered by the regulations may be treated as service on the taxpayer.

An old or unmonitored registered address creates serious risk. Failure to update BIR registration records after transferring or closing a business may allow service at the address in the BIR database to stand. Monitor mail at all registered and known business addresses while an audit is pending.

Treat the statutory periods as calendar-day deadlines and file early. Do not assume that an informal conversation, an unanswered request for an extension, or a holiday will automatically enlarge the period.

Choose the correct type of protest

The two administrative remedies are different and generally should not be mixed.

Request for reconsideration

Choose reconsideration when you ask the BIR to reevaluate the assessment using the evidence and records already on file. It may raise factual or legal issues, but it does not depend on new or additional evidence.

The separate 60-day supporting-document deadline does not apply to reconsideration. Nevertheless, the protest itself must already be complete enough to be valid. Labeling an incomplete holding letter as a request for reconsideration will not cure missing grounds or omitted issues.

Request for reinvestigation

Choose reinvestigation when you need the BIR to consider newly discovered or additional evidence.

The protest must specify the additional evidence you intend to present. You must submit all relevant supporting documents within 60 days from the protest’s filing date. The BIR’s evaluation may be limited to documents submitted within that period.

Use a dated transmittal letter listing every enclosure. Obtain a stamped receiving copy or other reliable proof identifying what was delivered and when.

A reinvestigation request may also affect the limitation period for collection only under particular statutory conditions, including whether the request was granted. Do not choose it merely in the hope of delaying collection; have its prescription effects reviewed against the documents and dates in your case.

What a valid protest should contain

A strong protest is organized issue by issue rather than written as a general denial.

Include:

Taxpayer information: Registered name, trade name if applicable, TIN, registered address, and contact details.
Assessment details: Assessment numbers, tax types, taxable periods, assessment dates, and amounts.
Material dates: Date each FLD/FAN was received and the resulting protest deadline.
Nature of the remedy: An express statement that the filing is a request for reconsideration or reinvestigation.
Scope: A clear statement identifying every finding and amount being disputed and any amount accepted.
Facts: A concise chronology and the transaction-level facts relevant to each finding.
Legal grounds: The applicable Tax Code provisions, regulations, treaties if relevant, and controlling jurisprudence.
Computations: A reconciliation showing the BIR computation, the taxpayer’s correction, and the resulting amount, if any.
Evidence: An indexed list of supporting documents. For reinvestigation, identify the new or additional evidence to be submitted.
Relief requested: Cancellation or reduction of the assessment, correction of the computation, withdrawal of penalties, or another precise result supported by law.
Authority and signature: The taxpayer’s signature or the proper corporate or representative authorization.
Attachments and proof of filing: Include the FLD/FAN and schedules, authority documents, evidence index, and a receiving copy.

A protest should expressly address every issue. Under RR No. 18-2013, an issue not disputed—or disputed without its supporting facts and legal basis—may be treated as undisputed. The corresponding assessment may then become final and collectible even while other issues remain under review.

A letter that merely asks for more time, promises to submit documents later, or says that the taxpayer “disagrees” may not be a valid protest. The Supreme Court emphasized the required contents of a protest in Commissioner of Internal Revenue v. Citysuper, Inc..

Where and how to file

File the PAN response or FLD/FAN protest with the duly authorized BIR representative who signed the relevant notice, through that official’s designated receiving or docket office. Revenue Memorandum Circular No. 11-2014 confirms this routing rule.

Before filing:

Check the assessment’s filing instructions.
Confirm the responsible office for regional, Large Taxpayers Service, or national investigation cases.
Bring enough copies to obtain a complete stamped receiving copy.
Ensure the stamp shows the date, office, and preferably the number of pages or attachments.
If using an officially accepted alternative method, retain proof that establishes timely receipt—not merely dispatch.
Do not rely on an ordinary email unless a current BIR issuance or written instruction expressly authorizes it for that filing.

Keep both a physical and secure digital copy of the complete submission.

Review possible procedural and substantive defenses

A timely protest should challenge both the merits and any material procedural defects supported by the record.

Authority to conduct the audit

Check the Letter of Authority and any replacement or reassignment documents. Relevant questions include:

Was an LOA issued by a duly authorized official?
Did it cover the correct taxpayer, period, and taxes?
Did the revenue officers who actually conducted the examination have authority?
Was a reassignment properly authorized?

The Supreme Court has repeatedly treated the LOA as the authority for designated revenue officers to examine a taxpayer, including in Commissioner of Internal Revenue v. McDonald’s Philippines Realty Corporation. The governing result depends on the exact audit documents and what each officer actually did.

Proper service and due process

Check whether the PAN, FLD/FAN, and FDDA were properly served and whether the BIR observed the required sequence and response periods. Preserve evidence concerning the recipient, address, and delivery method.

Even if you believe service or the assessment was void, file the protest within the earliest arguable deadline when reasonably possible. Relying only on a service objection can be dangerous if the BIR or a court later finds receipt valid.

Factual and computational errors

Reconcile the assessment against:

Filed returns and amended returns.
Audited financial statements.
General ledgers, journals, and subsidiary ledgers.
Invoices and other source documents.
Withholding tax certificates and alphalists.
Bank records and payment proofs.
Contracts, delivery records, and third-party confirmations.
Prior tax credits, carryovers, and payments.
The correct tax rate and taxable period.
Penalty and interest computations.

Do not submit large volumes of records without explaining what each document proves.

Prescription

As a general rule, internal revenue taxes must be assessed within three years from the later of the statutory filing deadline or the actual filing date. Different periods may apply to a false or fraudulent return with intent to evade tax, failure to file a return, or a valid written waiver of the limitation period. Sections 203 and 222 appear in the National Internal Revenue Code.

Prescription is document- and date-sensitive. Review the return, filing confirmation, LOA, notices, service records, waivers, and any events claimed to suspend the period.

What happens after filing

BIR action within 180 days

For a request for reconsideration, the 180-day period is generally counted from the filing of the protest. For a request for reinvestigation, RR No. 18-2013 counts it from submission of the required supporting documents.

Preserve the filing date and, for reinvestigation, the date and contents of the final documentary submission.

BIR inaction after 180 days

If the BIR does not act within the applicable 180-day period, the taxpayer generally has two mutually exclusive choices:

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

Choosing one path bars the other. Calculate the 180th and 30th days at the outset rather than waiting for them to approach. The Supreme Court confirmed the option to await the final decision in Lascona Land Co., Inc. v. Commissioner of Internal Revenue.

FDDA issued by an authorized BIR representative

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

An administrative appeal or request for reconsideration to the Commissioner of Internal Revenue; or
A petition for review with the CTA.

A request for reinvestigation is no longer available at this stage. Only matters properly raised and covered by the disputed decision should be expected to receive consideration.

Decision issued by the Commissioner

If the Commissioner denies the protest or administrative appeal, in whole or in part, 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 deadline.

When appealing an FDDA to the Commissioner or CTA, current BIR guidance also requires a copy of the appeal to be furnished within five days from filing to the Chief of the Assessment Division for regional cases, or to the concerned Head Revenue Executive Assistant for covered Large Taxpayers Service or national investigation cases. See the BIR’s official listing for RMC No. 43-2023.

Appealing to the Court of Tax Appeals

The CTA has exclusive appellate jurisdiction over CIR decisions and qualifying inaction in disputed assessments under Republic Act No. 9282.

A CTA appeal is judicial litigation, not another letter to the BIR. It normally begins with a petition for review before a CTA Division and must comply with the Revised Rules of the Court of Tax Appeals, including requirements on form, verification, attachments, filing fees, and service.

Engage Philippine tax litigation counsel well before the deadline. Counsel will need time to:

Confirm CTA jurisdiction and the exact appeal date.
Identify the decision or inaction being appealed.
Prepare the verified petition and certification against forum shopping.
Organize the assessment and administrative record.
Determine whether suspension of collection should be requested.
Arrange filing fees, service, witnesses, and documentary evidence.

An appeal to the CTA does not automatically suspend payment, levy, distraint, or sale. The CTA may suspend collection when the statutory standard is met and may require a deposit or surety bond of up to twice the amount claimed. This rule appears in Section 11 of RA No. 9282.

Evidence to preserve

Maintain a single assessment file containing:

The LOA and all reassignment or supplemental authority documents.
Requests for information, subpoenas, notices, and replies.
The PAN, FLD/FAN, FDDA, and all schedules.
Envelopes, registry receipts, courier records, and receiving logs.
Every protest and documentary transmittal with proof of filing.
Returns, financial statements, books, invoices, contracts, and payment records.
BIR computation sheets and the taxpayer’s reconciliations.
Board resolutions, secretary’s certificates, special powers of attorney, and tax-agent appointments.
Emails and meeting notes recording representations made by either side.
A master chronology showing every receipt, filing, and deadline.

Preserve original records. Work from copies unless the BIR lawfully requires originals, and document any originals temporarily surrendered.

Common mistakes

Treating a PAN response as the protest against the FLD/FAN.
Counting from the assessment date instead of the receipt date.
Filing only a holding letter or unsupported general denial.
Failing to identify reconsideration or reinvestigation.
Omitting one tax type, period, issue, or assessment number.
Reserving all arguments for later instead of stating the factual and legal bases now.
Choosing reinvestigation but missing the 60-day document deadline.
Submitting documents without an index, explanation, or proof of receipt.
Sending the protest to the wrong BIR office or relying on an unauthorized email.
Assuming discussions with examiners suspend statutory deadlines.
Waiting beyond the CTA deadline while asking the Commissioner to reconsider a final denial.
Appealing after 180 days without understanding that this choice is inconsistent with waiting for a later decision.
Ignoring notices delivered to a registered address, receptionist, employee, or appointed tax agent.
Assuming a protest or CTA appeal automatically stops interest or collection.
Paying a disputed portion without documenting whether the payment is a settlement, partial acceptance, or payment made while preserving available remedies.

When professional help is urgent

Seek a Philippine tax lawyer and qualified tax accountant immediately if:

Fewer than 10 days remain before a protest or CTA deadline.
The assessment is material to the taxpayer’s operations or solvency.
The BIR alleges fraud, falsified transactions, undeclared income, or failure to file.
A subpoena, collection letter, warrant of distraint or levy, garnishment notice, or criminal referral has been received.
The BIR has contacted customers, banks, suppliers, or officers.
The assessment involves related parties, transfer pricing, withholding taxes, VAT refunds or credits, treaty relief, or several taxable periods.
The audit was conducted by officers not named in the LOA.
The taxpayer did not receive one or more required notices.
An FDDA has been issued or the 180-day period is about to expire.
Payment, compromise, or settlement is being considered.

Frequently asked questions

Must I pay the assessment before filing an administrative protest?

Ordinarily, payment is not a prerequisite to a timely administrative protest. Any undisputed portion may become final and demandable, however, and interest or other lawful increments may continue. Obtain advice before making a partial payment because it can affect the remaining dispute and the relief requested.

Can the BIR extend the 30-day protest deadline?

Do not rely on an extension. The 30-day period is treated as mandatory, and an assessment not validly protested on time generally becomes final, executory, and demandable.

Can I submit a short protest now and give the reasons later?

That is unsafe. A valid protest must already identify the remedy and state the relevant factual and legal grounds. For reinvestigation, additional evidence may be submitted within 60 days, but the initial protest still must satisfy the validity requirements.

What if only part of the assessment is wrong?

Identify the disputed and accepted portions precisely. An undisputed issue or an issue unsupported by facts and law may become final and collectible even if other portions remain under protest.

What if I never received the PAN?

Raise the lack or invalidity of service in the protest, unless the assessment falls within a statutory exception to the PAN requirement. Preserve evidence of the registered address, office receiving procedures, and actual delivery history.

What if the BIR never decides my protest?

After the applicable 180-day period, either appeal the inaction to the CTA within the following 30 days or wait for a final decision and appeal within 30 days from receiving it. The choices are mutually exclusive.

Can I go directly to the CTA after receiving a PAN?

Generally, no. A PAN is proposed rather than final. The usual route is to respond to the PAN, protest the resulting FLD/FAN, and appeal the FDDA or qualifying BIR inaction.

Does a timely protest stop all collection activity?

A timely valid protest prevents the disputed assessment from becoming final merely because the 30-day protest period expired. Collection questions can nevertheless become complex, particularly after an FDDA or during a CTA appeal. An appeal to the CTA does not automatically suspend collection, so collection notices require immediate legal attention.

Official legal sources

This article provides general Philippine legal information, not legal or tax advice for a particular assessment. Outcomes depend on the notices, proof of receipt, audit authority, taxable periods, evidence, and procedural history. Official sources and procedures were checked as of July 23, 2026.