Quick answer

You protest a BIR deficiency assessment by filing a valid written request for reconsideration or reinvestigation within 30 calendar days from receipt of the Formal Letter of Demand and Final Assessment Notice (FLD/FAN). File it with the BIR office or duly authorized official identified in the notice, address every disputed issue, cite the supporting law and facts, and keep conclusive proof of timely filing.

If you choose reinvestigation, submit all relevant supporting documents within 60 calendar days from filing the protest. If the BIR denies the protest, or does not act within the applicable 180-day period, an appeal to the Court of Tax Appeals (CTA) generally must be made within 30 days. Missing any of these periods can make the assessment final, executory, and demandable.

A response to a Notice of Discrepancy or Preliminary Assessment Notice is important, but it does not replace the separate 30-day protest required after receiving the FLD/FAN.

The controlling framework is Section 228 of the National Internal Revenue Code, implemented principally by Revenue Regulations No. 18-2013, which amended RR No. 12-99.

Identify the document you received

Different BIR documents trigger different remedies and deadlines.

Document or event	What it means	Immediate action
Letter of Authority (LOA)	Authorizes named revenue officers to examine specified tax periods	Verify the covered taxpayer, taxes, periods, officers, and authority
Notice of Discrepancy (NOD)	Preliminary audit findings; not yet the final assessment	Participate in the Discussion of Discrepancy and present explanations and documents within the applicable 30-day process
Preliminary Assessment Notice (PAN)	Proposed deficiency assessment	Submit a detailed written response within 15 days from receipt
FLD/FAN	Formal deficiency assessment and demand for payment	File the administrative protest within 30 days from receipt
Final Decision on Disputed Assessment (FDDA)	Decision on the protest	Determine who signed it and appeal within the applicable 30-day period
Collection letter, Final Notice Before Seizure, warrant of distraint or levy, or garnishment	The BIR is treating the liability as collectible	Obtain legal help immediately and verify whether a valid, final assessment exists

Do not rely only on the document’s label. Its language, issuing authority, demand for payment, and statement that it is a final decision may determine the available remedy. When in doubt, treat the earliest plausible deadline as controlling.

The assessment timeline

1. Notice of Discrepancy

Under RR No. 22-2020, the Notice of Discrepancy replaced the former Notice for Informal Conference. It gives the taxpayer an opportunity to discuss the audit findings and present supporting records before a PAN is issued. The Discussion of Discrepancy should not extend beyond 30 days from receipt of the NOD.

Attend the scheduled discussion or give prompt written notice if attendance is impossible. Submit reconciliations, source documents, and legal explanations early. The BIR’s prescribed NOD format is covered by Revenue Memorandum Circular No. 102-2020.

2. Preliminary Assessment Notice

The general rule is that the BIR must issue a PAN stating in detail the facts and legal bases for the proposed assessment. The taxpayer has 15 days from receipt to respond.

A PAN is not required in the five situations listed in Section 228:

A mathematical error appears on the face of the return.
Tax withheld differs from the amount remitted by the withholding agent.
Excess creditable withholding tax claimed for refund or tax credit was also carried over to succeeding quarters.
Excise tax on excisable articles was not paid.
An article bought or imported tax-free by an exempt person was transferred to a non-exempt person.

In those cases, the BIR may issue the FLD/FAN directly.

Responding to the PAN is still worthwhile even when the same issues were discussed at the NOD stage. It creates a clear record of the taxpayer’s facts, evidence, and legal objections. But a PAN response is not the formal protest contemplated by Section 228.

3. Formal Letter of Demand and Final Assessment Notice

The FLD/FAN must state the relevant facts and the law, regulations, or jurisprudence on which the assessment rests. A conclusory computation without an adequate factual and legal explanation may violate statutory due process. The Supreme Court has repeatedly treated these requirements as substantive, not cosmetic. See, for example, CIR v. Avon Products Manufacturing, Inc..

Even when the assessment appears defective, do not ignore it. Raise the defect in a timely protest while preserving every substantive defense. Whether service, authority, or explanation was legally sufficient may itself become contested.

The 30-day administrative protest

File the protest no later than 30 calendar days from actual or legally effective receipt of the FLD/FAN.

The protest must expressly state:

Whether it is a request for reconsideration or request for reinvestigation.
The date of the assessment notice.
The applicable law, regulations, or jurisprudence supporting the protest.
For each disputed issue, the material facts and the reason the BIR’s conclusion or computation is incorrect.
For a reinvestigation, the newly discovered or additional evidence that will be presented.

A generic letter saying that the taxpayer “disagrees,” is still gathering documents, or reserves the right to submit arguments later may not be a valid protest. In CIR v. Citysuper, Inc., the Supreme Court emphasized compliance with the protest requirements prescribed by RR No. 18-2013.

Include, as good practice:

Taxpayer’s registered name, TIN, and registered address.
Assessment numbers, tax types, and taxable periods.
Dates the FLD/FAN and attachments were received.
Amounts disputed and any amounts admitted.
A separate discussion of every assessment item.
A numbered annex list and reconciliation to the BIR computation.
Proof that the signatory or representative is authorized.

If only some issues are protested—or if some issues are listed without supporting facts and law—the unchallenged portions may become final and collectible. Clearly identify every disputed item.

Reconsideration or reinvestigation?

Request for reconsideration

Choose reconsideration when the BIR can resolve the protest using the records already submitted. It may involve questions of fact, law, or both, but does not require new evidence.

For reconsideration, the BIR’s 180-day period generally runs from the filing of the protest. The separate 60-day document period does not apply.

Request for reinvestigation

Choose reinvestigation when you need the BIR to consider newly discovered or additional evidence. Identify that evidence in the protest and submit all relevant supporting documents within 60 calendar days from filing the protest.

The BIR’s 180-day period runs from the submission of the required supporting documents, provided they are submitted within the 60-day window.

The substance of the request matters more than its caption. If your case depends on new invoices, reconciliations, contracts, certificates, or accounting schedules, calling it “reconsideration” may create uncertainty about the applicable periods. State the chosen remedy and its evidentiary basis plainly.

The BIR must respect the full 60-day period in a proper reinvestigation. In CIR v. Maxicare Healthcare Corporation, the Supreme Court held that prematurely deciding the protest before that period expired deprived the taxpayer of a real opportunity to present supporting documents.

Where and how to file

BIR guidance directs taxpayers to file the protest with the duly authorized representative who signed the PAN and FLD/FAN. An administrative appeal from that representative’s decision is filed with the Office of the Commissioner. See RMC No. 11-2014.

Before filing:

Read the FLD/FAN’s filing instructions and identify the issuing office and signatory.
Confirm the office’s current receiving location and accepted filing method.
Do not assume that sending an ordinary email is a legally sufficient protest unless an applicable issuance or written instruction expressly authorizes it.
If filing personally, obtain a complete stamped-received copy showing the date, receiving office, and receiving officer.
If another authorized method is used, retain the official receipt, tracking record, transmitted file, acknowledgment, and complete copy of everything sent.
Preserve evidence of any office closure or technical failure.

The periods are stated in calendar days. As a conservative practice, exclude the date of receipt and include the final day, but file well before the deadline. Do not assume that every Saturday, Sunday, office closure, or work-from-home day automatically extends a BIR deadline.

A limited current exception exists for certain National Office filings affected by the 2026 government energy-conservation arrangement: RMC No. 35-2026 moves a Friday deadline to the next business day for a request for reconsideration of an FDDA, while that arrangement remains in force. It should not be generalized to other BIR filings.

Build the protest issue by issue

An effective protest connects each BIR finding to the controlling facts, source records, and law. Depending on the assessment, review:

Whether the BIR used the correct taxpayer, tax type, taxable period, rate, and tax base.
Whether payments, withholding tax credits, input VAT, carryovers, or previously assessed amounts were credited.
Whether alleged undeclared sales are actually loans, advances, reimbursements, intercompany transfers, exempt receipts, or timing differences.
Whether deductions or input taxes are supported by the documents legally required for the period involved.
Whether the BIR relied on third-party data without reconciling cancellations, returns, duplicate reports, withholding entries, or accounting cutoffs.
Whether the assessment was issued within the applicable prescriptive period.
Whether the audit was conducted by revenue officers properly authorized under a valid LOA.
Whether the NOD, PAN, FLD/FAN, and FDDA were properly issued, served, and explained.
Whether the assessment changed theories or factual bases without giving the taxpayer a meaningful opportunity to respond.
Whether penalties or allegations of fraud have an adequate factual and legal basis.

The ordinary period to assess is generally three years, subject to statutory exceptions and valid waivers. The extraordinary 10-year period for a false return requires a deliberate or willful misstatement; mere error or understatement does not automatically establish it. The Supreme Court explained these standards in CIR v. McDonald’s Philippines Realty Corporation. Prescription calculations are document- and date-sensitive, so have them checked carefully.

Evidence to preserve

Keep original documents safe and create a complete, searchable duplicate set containing:

LOA and notices of assignment or reassignment.
NOD, PAN, FLD/FAN, FDDA, computation sheets, and schedules.
Envelopes, registry notices, courier records, email headers, and proofs of receipt.
All responses, protests, annexes, stamped copies, and filing acknowledgments.
Tax returns, amended returns, payment confirmations, and withholding certificates.
Books of account, ledgers, journals, trial balances, and audit working papers.
Invoices, official receipts applicable to the period, contracts, purchase orders, and delivery records.
Bank statements, remittance records, and payment reconciliations.
Government registrations, exemption or incentive documents, and rulings relied upon.
Minutes or written summaries of meetings with the BIR.
Powers of attorney, board resolutions, or other authority documents.
A master chronology showing every receipt, filing, and deadline.

Do not alter source records or create backdated documents. If an explanation requires a reconstruction, label it honestly and show the underlying data.

What happens after filing?

Denial by a duly authorized representative

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

File a petition for review with the CTA; or
Elevate the protest to the Commissioner through a request for reconsideration.

The administrative appeal to the Commissioner is limited to reconsideration; a new reinvestigation is not allowed, and only issues covered by the authorized representative’s decision will be entertained.

Denial by the Commissioner

File the CTA petition within 30 days from receipt. A further motion for reconsideration filed with the Commissioner does not suspend or restart the 30-day CTA period.

BIR inaction for 180 days

If the applicable 180-day period expires without a decision, choose between:

Appealing the inaction to the CTA within 30 days after the 180-day period expires; or
Waiting for the BIR’s final decision and appealing within 30 days from receipt of that decision.

These options are mutually exclusive. Once the taxpayer chooses and pursues one route, the other cannot be used to cure a late or unsuccessful appeal. The rule is discussed in RCBC v. CIR and Lascona Land Co., Inc. v. CIR.

If you decide to wait, document that choice consistently. Continue monitoring mail, the registered address, the authorized tax agent, and every BIR communication.

Appealing to the Court of Tax Appeals

A disputed national tax assessment is appealed to a CTA Division through a petition for review, not through an ordinary civil complaint in a Regional Trial Court.

The petition generally must:

Be filed within the applicable 30-day period.
Be verified.
Contain a certification against forum shopping.
Establish the CTA’s jurisdiction and show the material dates.
State the complete facts, issues, errors, and requested relief.
Attach a clearly legible duplicate original or certified true copy of the decision appealed from.
Comply with docket-fee, service, copy, and current electronic-submission requirements.

The governing requirements appear in the Revised Rules of the Court of Tax Appeals. Current electronic-copy specifications are addressed in CTA En Banc Resolution No. 8-2024.

Treat the 30-day period as a hard deadline. CTA litigation is technical and ordinarily requires tax counsel to prepare the petition, evidence, and any request for interim relief.

Collection while the case is disputed

A timely administrative protest generally prevents the disputed assessment from becoming final merely because the FLD/FAN demanded payment. A timely administrative appeal to the Commissioner likewise prevents the authorized representative’s decision from becoming final while that appeal remains pending.

After an appeal reaches the CTA, however, filing the petition does not automatically suspend collection. The taxpayer may ask the CTA to suspend collection when collection may jeopardize the interests of the government or the taxpayer. The court may require a cash deposit or an acceptable surety bond of not more than twice the disputed amount. The motion requires evidence and a hearing; it is not granted automatically.

The Supreme Court has also held that collection action taken before the 30-day period to appeal an FDDA has expired may improperly defeat the statutory right to judicial review. See CIR v. CTA Second Division and American Wire and Cable Co., Inc..

Common mistakes

Treating a PAN response as the required protest against the later FLD/FAN.
Filing a placeholder letter that omits the protest type, assessment date, legal bases, or issue-specific facts.
Protesting only the total amount without addressing each assessment item.
Choosing reinvestigation but missing the 60-day document deadline.
Sending the protest to the wrong BIR office or relying on unacknowledged email.
Failing to preserve proof of receipt and filing.
Allowing an unauthorized employee or adviser to sign the protest.
Leaving some assessment items undisputed by accident.
Computing the 180 days from the wrong event.
Filing another motion with the Commissioner after the Commissioner’s denial and assuming it stops the CTA deadline.
Appealing BIR inaction late, then trying to switch to the “await the final decision” route.
Assuming a CTA appeal automatically stops distraint, levy, or garnishment.
Waiting for a collection notice before seeking professional help.

When help is urgent

Consult a Philippine tax lawyer promptly if:

The 30-day protest or CTA deadline is approaching or may already have expired.
You received an FDDA, Final Notice Before Seizure, warrant of distraint or levy, garnishment notice, or bank account freeze.
The BIR alleges fraud, falsity, willful failure, or criminal tax violations.
No PAN or FLD/FAN appears to have been validly served before collection began.
The assessment involves several tax types, multiple years, related parties, incentives, cross-border transactions, or substantial exposure.
The assessment relies on third-party information you cannot readily reconcile.
The BIR disregarded documents already submitted or decided a reinvestigation before the 60-day evidence period expired.
The signatory, LOA, service, or prescriptive period appears defective.

A collection effort unsupported by a valid assessment may be challengeable, but the remedy and deadline depend on the documents actually issued. In CIR v. Stradcom Corporation, the Supreme Court reiterated that collection of a disputed deficiency generally requires a valid assessment issued with statutory due process.

FAQ

Must I pay the assessment before protesting?

Generally, no. An administrative protest under Section 228 is not a pay-before-protest procedure. Any portion you do not validly dispute may nevertheless become final and should be addressed separately.

Can I protest only the PAN?

You should respond to the PAN, but if the BIR later issues an FLD/FAN, you must file a separate valid protest within 30 days. The earlier response does not carry over automatically.

Can I submit supporting documents after 60 days?

A reinvestigation must be supported within 60 days from filing the protest. Late submission can cause the taxpayer to lose the right to dispute the assessment through additional evidence. Do not rely on an informal extension unless it has a clear legal basis and written confirmation.

What if the BIR never decides my protest?

After the applicable 180-day period, either appeal the inaction to the CTA within the next 30 days or wait for the final decision. Record the choice carefully because the remedies are mutually exclusive.

Is an email protest valid?

Do not assume so. Use only a filing method authorized for that office and document. Obtain an official acknowledgment showing timely receipt of the complete protest and annexes.

Does appealing to the CTA stop collection?

No, not automatically. A separate, evidence-supported motion to suspend collection may be necessary.

What if I received a warrant or collection letter but never received an FLD/FAN?

Seek help immediately. Verify the registered address, authorized agent, service records, and BIR case docket. The absence of a valid assessment can be a serious due-process issue, but receipt and service are factual matters that require evidence.

Official sources

This article provides general legal information, not legal or tax advice for a particular assessment. Deadlines and remedies depend on the notices, proof of receipt, issuing authority, tax period, and procedural history. Sources and current procedures were checked as of August 3, 2026.