Quick answer

To contest a BIR deficiency assessment, file a valid written request for reconsideration or reinvestigation within 30 days from receipt of the Formal Letter of Demand and Final Assessment Notice (FLD/FAN). File it with the office of the Commissioner of Internal Revenue’s authorized representative who signed the assessment, following the filing instructions in the notice.

The protest must identify the assessment, expressly choose the type of protest, and state the facts and legal grounds for every disputed issue. If you choose reinvestigation, submit all relevant supporting documents within 60 days from filing the protest. Missing these deadlines can make the assessment final, executory, and demandable.

There is no minimum peso amount required to use this procedure. The governing rule is Section 228 of the National Internal Revenue Code, implemented principally by Revenue Regulations No. 18-2013.

First identify what you received

Not every BIR communication starts the 30-day protest period.

BIR document	What it generally means	Usual response period
Notice of Discrepancy (NOD)	Initial audit findings; not yet the final assessment	Explain the discrepancies and submit supporting documents within 30 days from receipt
Preliminary Assessment Notice (PAN)	Proposed deficiency assessment	Submit a written reply within 15 days from receipt
FLD/FAN	Formal demand and final assessment	File the Section 228 protest within 30 days from receipt
Final Decision on Disputed Assessment (FDDA)	Decision on the administrative protest	Take the proper administrative appeal or file with the CTA within 30 days, as applicable
Consolidated FAN	A 2026 consolidated assessment that supersedes specified earlier FANs	A fresh 30-day protest period runs from receipt, if issued under the applicable consolidation rules

The formal protest is directed against the FLD/FAN, not merely the PAN. A reply to a PAN does not replace the protest required after receipt of the FLD/FAN. The Supreme Court has repeatedly treated compliance with the assessment process as a substantive due-process requirement, while also requiring taxpayers to use the administrative protest remedy on time.

Under Revenue Regulations No. 22-2020, the NOD and discussion-of-discrepancy stage generally precede the PAN. Use that stage to correct factual errors and submit records early, but continue watching for the PAN and FLD/FAN.

Record the date of receipt immediately

The most important factual question is often: When was the notice received, and by whom?

Preserve:

The original envelope, registry notice, return card, or courier pouch
The receiving copy showing the date, name, signature, and position of the recipient
Courier tracking records and proof of delivery
Your office receiving log, email routing records, and scanned copy of the notice
Any proof that the notice was sent to an outdated, incorrect, or unregistered address
The written authority of any tax agent or representative who received it

BIR notices may be served personally, by substituted service, or by mail or professional courier under RR No. 18-2013. Service on a duly appointed tax agent or practitioner may be treated as service on the taxpayer. Refusing delivery is therefore unsafe and may not prevent effective service.

As a general computation rule, exclude the day of receipt and include the last day. If the last day falls on a Saturday, Sunday, or legal holiday, the period ordinarily moves to the next working day under Rule 22 of the Rules of Court. Do not assume that office closures, ongoing discussions, or a request for more time automatically extend a statutory deadline. Disaster or force-majeure extensions apply only when covered by a specific BIR issuance.

Choose the correct kind of protest

Request for reconsideration

A request for reconsideration asks the BIR to reevaluate the assessment using the records already available. It may involve questions of fact, law, or both, but does not depend on newly discovered or additional evidence.

The separate 60-day document-submission period does not apply. The BIR’s 180-day action period is generally counted from the filing of the protest.

This route may fit when the record is already complete and the dispute concerns matters such as:

An error in applying a tax provision
Double counting or an arithmetic mistake evident from existing records
Misclassification of a transaction
Failure to credit payments or withholding certificates already submitted
Prescription or another legal defect shown by the existing record

Request for reinvestigation

A request for reinvestigation asks the BIR to reevaluate the assessment using newly discovered or additional evidence.

The protest must expressly say that it is a request for reinvestigation and identify the additional evidence you intend to present. All relevant supporting documents must be submitted within 60 days from filing the protest. The BIR’s 180-day action period is generally counted from submission of the required documents.

Do not rely on language such as “we are still compiling documents.” In CIR v. Court of Tax Appeals, G.R. No. 239464, the Supreme Court held that language implying reinvestigation did not cure the failure to choose it expressly. In CIR v. Maxicare Healthcare Corporation, the Court confirmed that the 60-day period concerns a reinvestigation protest against the FLD/FAN—not the earlier response to the PAN.

What the protest should contain

A valid protest should, at minimum:

Identify the taxpayer by full registered name, TIN, registered address, and contact details.
Identify the FLD/FAN by date, assessment numbers, tax types, taxable periods, and assessed amounts.
State the exact date the FLD/FAN was received.
State expressly whether the protest is a request for reconsideration or request for reinvestigation.
For reinvestigation, identify the newly discovered or additional evidence to be submitted.
Address each assessment issue separately.
State the material facts supporting the taxpayer’s position on each issue.
Cite the applicable statutes, regulations, and controlling jurisprudence for each ground.
Explain the correction requested and, where possible, show the taxpayer’s recomputation.
List and label all attachments.
Request cancellation or reduction of the assessment and issuance of the appropriate decision.
Be signed by the taxpayer or a properly authorized representative.

A bare statement that the taxpayer “disagrees” or “protests the assessment” is not enough. RR No. 18-2013 makes the prescribed contents material to the protest’s validity.

If the FLD/FAN contains several issues, dispute every issue you intend to contest. An issue that is omitted—or for which no factual and legal grounds are stated—may be treated as undisputed. The corresponding amount can become final, executory, and demandable even while other issues remain under protest.

Build an issue-by-issue evidence file

Prepare a working schedule with one row for each assessment issue:

Issue	BIR position	Taxpayer’s facts	Legal ground	Evidence	Correct amount

Depending on the issue, preserve and organize:

Filed returns, amendments, confirmation receipts, and payment records
Books of accounts, journals, ledgers, trial balances, and audit trails
Invoices and other source documents
Certificates of creditable or final withholding tax
Contracts, purchase orders, delivery records, and proof of performance
Bank statements, remittance records, and reconciliations
Payroll records and employee documentation
Importation, customs, and excise-tax records
Board resolutions and corporate secretary’s certificates
Correspondence with customers, suppliers, and BIR personnel
The Letter or electronic Letter of Authority and any replacement authority
NOD, PAN, replies, FLD/FAN, schedules, protest, document transmittals, FDDA, and collection notices
Proof of every submission to and receipt by the BIR

Use indexed annexes and retain an exact electronic and paper copy of everything filed. If voluminous records are submitted, include an inventory stating the document description, date range, and number of pages or files.

Where and how to file

BIR guidance directs taxpayers to file the protest with the office of the authorized representative who signed the FLD/FAN. RMC No. 11-2014 and RMC No. 39-2013 address this filing route.

For a defensible filing:

Follow the office and addressee stated in the FLD/FAN.
If filing personally, obtain a stamped receiving copy showing the date, time, office, recipient, and complete list of attachments.
If using registered mail, retain the registry receipt, return card, envelope copy, and complete duplicate of the submission.
Do not rely solely on ordinary email, a message to the revenue officer, or delivery to an unrelated RDO counter unless a controlling issuance or written case-specific instruction authorizes that method.
Include the representative’s special power of attorney, board resolution, secretary’s certificate, or other required authority.
File early enough to correct a rejected or misdirected submission before the deadline.

A stamped copy of only the cover letter is less useful if it does not show what documents accompanied it. Have the receiving copy refer expressly to an attached annex index.

Check whether the assessment itself followed due process

A timely protest should raise every procedural and substantive defect supported by the record. Possible issues include:

Absence of a valid Letter of Authority or examination by persons not properly authorized
Failure to issue or properly serve a required NOD, PAN, FLD/FAN, or supporting schedule
Failure to state the factual and legal bases of the assessment
Material differences between the PAN and FLD/FAN that were not properly explained
Failure to consider the taxpayer’s explanations and evidence
Assessment or collection outside the applicable prescriptive period
Incorrect taxpayer, taxable period, tax type, computation, or payment credit
Improper service or signature by an official without the necessary authority

Section 228 requires the taxpayer to be informed in writing of both the law and the facts on which the assessment is based. An assessment that does not satisfy this requirement may be void. The Supreme Court discusses this requirement in CIR v. Liquigaz Philippines Corporation and CIR v. Yumex Philippines Corporation.

A procedural defect should still be raised through a timely protest and, when necessary, a timely CTA appeal. Do not simply ignore an assessment because you believe it is void.

When a PAN may be skipped

The general rule is that a PAN must precede the FLD/FAN. Section 228 permits an outright FLD/FAN, however, when:

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

Outside these exceptions, failure to issue and serve the required PAN can be a serious due-process issue.

The 2026 rule on a Consolidated FAN

Under the BIR’s Single-Instance Audit Framework, certain pending audits for the same taxpayer and taxable year may be consolidated. RMO No. 6-2026 generally prohibits consolidation once an FDDA has been issued or a FAN has become final and executory. Permitted FAN-level consolidation requires specified safeguards.

A valid Consolidated FAN must identify and supersede the covered earlier FANs. A fresh 30-day protest period runs from receipt of the Consolidated FAN. Do not assume that an earlier protest automatically satisfies the new requirement. Review the consolidated amounts and issues and file a complete protest against the Consolidated FAN within the new period.

What happens after filing

If the authorized representative denies the protest

When the denial is issued by the Commissioner’s duly authorized representative, the taxpayer generally has 30 days from receipt to choose between:

Filing a petition for review with the Court of Tax Appeals; or
Elevating the matter to the Commissioner through a request for reconsideration.

No reinvestigation is allowed in this administrative appeal, and only issues covered by the authorized representative’s decision may be entertained.

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 that 30-day judicial-appeal period.

If the BIR does not act within 180 days

The 180-day period is generally counted:

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

After the period expires without a decision, the taxpayer has two mutually exclusive choices:

Appeal the BIR’s inaction to the CTA within 30 days after the 180-day period expires; or
Continue waiting for the final decision, then appeal an adverse decision within 30 days from receipt.

The Supreme Court recognized the option to await a decision in Lascona Land Co. v. CIR. The choice should nevertheless be made deliberately with tax-litigation counsel because it determines the operative CTA deadline.

A CTA appeal does not automatically stop collection

A CTA appeal is made by filing a petition for review before a CTA Division within the applicable 30-day period. The deadline is jurisdictional and should not be entrusted to continuing settlement discussions.

Under Republic Act No. 9282, an appeal generally does not by itself suspend payment, levy, distraint, or sale of property. The CTA may suspend collection when collection may jeopardize the interests of the government or taxpayer, potentially subject to a deposit or surety bond of no more than twice the amount claimed.

Seek immediate advice if the BIR issues a warrant of distraint or levy, a garnishment notice, a collection letter, or another enforcement notice while the assessment remains disputed.

Common mistakes to avoid

Treating a PAN reply as the protest against the later FLD/FAN
Filing even one day after the 30-day period
Sending a vague “protest” without choosing reconsideration or reinvestigation
Failing to state factual and legal grounds for each assessment issue
Choosing reinvestigation but missing the 60-day document deadline
Filing with the examiner or wrong office instead of the office of the FLD/FAN signatory
Relying on email without an authorized filing procedure
Failing to obtain proof of filing and a complete attachment inventory
Assuming conferences, settlement discussions, or verbal assurances stop a deadline
Filing another motion with the Commissioner and assuming it tolls the CTA period
Ignoring an assessment because it appears procedurally defective
Failing to file a fresh protest after receiving a Consolidated FAN
Waiting beyond the 180-day period without documenting which appeal option was chosen

When professional help is urgent

Contact a Philippine tax lawyer promptly when:

Fewer than 10 days remain in a protest or CTA period
The date or validity of service is disputed
The assessment alleges fraud, deliberate falsity, or non-filing
A criminal referral, subpoena, or enforcement action is threatened
A warrant of distraint or levy, bank garnishment, or collection case has been issued
The assessment involves several tax types or taxable periods
The BIR personnel who conducted the audit may not have been properly authorized
Prescription depends on waivers or disputed filing dates
You received an FDDA, adverse Commissioner decision, or Consolidated FAN
The amount could threaten payroll, business operations, property, or banking relationships

A CPA can be essential for reconciliation and computation, but CTA litigation and urgent collection remedies require a lawyer admitted to Philippine practice.

Frequently asked questions

Can I ask for an extension of the 30-day protest period?

Do not rely on one. Section 228 sets the protest period, and ordinary requests or negotiations do not extend it. File a legally sufficient protest within 30 days.

Do I have 60 additional days in every case?

No. The 60-day period applies to a request for reinvestigation involving additional evidence. It does not apply to a request for reconsideration based on the existing record.

Can I protest only part of the assessment?

Yes, but the undisputed portions become final, executory, and demandable. Clearly identify every disputed and undisputed item and verify the allocation of payments, interest, and penalties.

What if the FLD/FAN does not explain the assessment?

Raise the lack of factual and legal bases in a timely protest. Section 228 makes adequate written notice mandatory, but the apparent defect is not a safe reason to ignore the assessment.

What if I never received a PAN?

A PAN is generally required unless one of the five statutory exceptions applies. Preserve all service evidence and raise the issue in the protest.

Can I go directly to the CTA after receiving the FLD/FAN?

Generally, no. The taxpayer must first file the administrative protest required by Section 228. Failure to exhaust that remedy can prevent CTA review, as emphasized in CIR v. Transitions Optical Philippines, Inc..

Does paying the assessment end every possible remedy?

Payment can materially change the remedy, including whether the matter must proceed as a refund or tax-credit claim with separate deadlines. Obtain advice before paying a disputed assessment or signing a compromise, waiver, or quitclaim.

Should I keep negotiating after an FDDA?

Negotiations may continue, but they do not protect the CTA deadline. Calendar and comply with the 30-day judicial-appeal period unless a qualified lawyer confirms another controlling remedy.

Official references

This article provides general Philippine legal information, not legal or tax advice for a particular assessment. Outcomes depend on the actual notices, service records, audit authority, documents, tax periods, and procedural history. Sources and procedures were checked as of July 23, 2026.