Quick answer

If you received a Formal Letter of Demand and Final Assessment Notice (FLD/FAN), file a valid written administrative protest within 30 days from receipt. Missing that deadline generally makes the assessment final, executory, and demandable.

Your protest must identify whether you seek reconsideration or reinvestigation, state the assessment date, and explain the factual and legal basis for disputing each finding. If you choose reinvestigation, identify the new or additional evidence and submit all relevant supporting documents within 60 days from filing the protest.

A Preliminary Assessment Notice (PAN) is different: respond within 15 days from receipt, but the formal 30-day protest is directed against the FLD/FAN. These periods are strict under Section 228 of the National Internal Revenue Code and BIR Revenue Regulations No. 18-2013.

Know which document you received

Different BIR documents trigger different remedies. Do not rely only on the document’s title; read its substance, demand language, issuer, and instructions.

Document	What it generally means	Immediate action
Notice of Discrepancy or audit findings	The audit remains at an earlier stage	Reconcile the figures, answer in writing, and preserve submissions
PAN	Proposed deficiency assessment	Submit a detailed response within 15 days from receipt
FLD/FAN	Final assessment and demand for payment	File a valid administrative protest within 30 days from receipt
Consolidated FAN	A replacement assessment issued under the 2026 audit-consolidation rules	Check whether it expressly supersedes earlier FANs and whether a fresh 30-day period applies
FDDA	Final Decision on Disputed Assessment	Within 30 days, take the proper administrative or CTA remedy depending on who issued it
Collection letter, Final Notice Before Seizure, or Warrant of Distraint and/or Levy	Collection action may have begun or the BIR may consider the assessment final	Obtain tax counsel immediately; do not assume an earlier protest remains pending

Record the date, time

Quick answer

Do not confuse the FLD/FAN with a Preliminary Assessment Notice (PAN). A PAN is ordinarily answered within 15 days from receipt; the formal 30-day protest is filed against the FLD/FAN.

Your protest must:

Choose either reconsideration or reinvestigation.
Identify the assessment and every disputed issue.
State the facts and the applicable law, regulations, or jurisprudence supporting each objection.
Attach or properly identify the evidence supporting your position.
Be filed with the proper BIR office, with reliable proof of timely receipt.

A request for reinvestigation gives you up to 60 days from filing the protest to submit relevant newly discovered or additional evidence. If the BIR denies the protest—or does not act within the applicable 180-day period—strict 30-day appeal rules apply.

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

Identify the document you received

The document’s substance, not merely its label, determines what action is required.

Document or event	General action	General deadline
Notice of Discrepancy or audit discussion	Explain and reconcile findings; preserve submissions	Follow the notice
Preliminary Assessment Notice (PAN)	Submit a detailed written reply	15 days from receipt
FLD/FAN	File a valid administrative protest	30 days from receipt
Reinvestigation protest	Submit all relevant supporting documents	60 days from filing the protest
Denial by an authorized BIR representative	Appeal to the CTA or elevate to the Commissioner	30 days from receipt
Denial by the Commissioner	Appeal to the CTA	30 days from receipt
BIR inaction	Choose between appealing the inaction or awaiting a final decision	See the 180-day rules below

Record the exact date, time, place, and manner of receipt. Keep the envelope, registry notice, courier record, email headers if officially transmitted electronically, and any receiving log signed by an employee.

A notice received by office personnel, a clerk, or another person at the taxpayer’s registered or known address may potentially constitute effective service. Refusing delivery or leaving BIR correspondence unopened is dangerous.

Responding to a Preliminary Assessment Notice

A PAN ordinarily gives the taxpayer 15 days from receipt to respond. The reply should address every proposed adjustment and include supporting reconciliations and documents.

The PAN must show in detail the factual and legal basis of the proposed assessment. However, the BIR may issue an FLD/FAN without a PAN in the specific cases listed in Section 228:

A mathematical error appearing on the face of the return.
A discrepancy between tax withheld and the amount 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 succeeding estimated liabilities.
Unpaid excise tax on excisable articles.
An article acquired or imported by an exempt person was sold, traded, or transferred to a non-exempt person.

Therefore, absence of a PAN does not automatically invalidate every assessment. Check whether a statutory exception actually applies.

A reply to a PAN is important, but it does not replace the 30-day protest against a later FLD/FAN.

Choose the correct kind of protest

The protest must expressly state whether it is a request for reconsideration or reinvestigation.

Request for reconsideration

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

The special 60-day document-submission period does not apply to reconsideration. Submit the complete factual and legal support with the protest rather than assuming that evidence may be added later.

Request for reinvestigation

A reinvestigation asks for reevaluation based on newly discovered or additional evidence. The protest must specify the evidence you intend to present.

All relevant supporting documents must be submitted within 60 days from filing the protest. Under RR No. 18-2013, failure to comply bars the taxpayer from disputing the assessment through newly discovered or additional evidence and leads to denial through a Final Decision on Disputed Assessment.

Choose based on the actual record. Calling a submission “reconsideration” while promising documents that were never previously presented can create a serious procedural problem.

What the protest should contain

A bare statement such as “we disagree,” “we request reconsideration,” or “documents will follow” is not a safe or valid protest.

Include at least:

The taxpayer’s complete registered name, address, and TIN.
The assessment number, date, tax type, taxable period, and assessed amount.
The date and manner the FLD/FAN was received.
An express statement that the letter is a protest under Section 228.
The chosen remedy: reconsideration or reinvestigation.
For reinvestigation, a specific description of the newly discovered or additional evidence to be submitted.
A table separating disputed and undisputed findings and amounts.
For each disputed finding:
- the BIR’s position;
- the relevant facts;
- the taxpayer’s computation;
- the applicable statutory, regulatory, and jurisprudential basis; and
- the supporting exhibits.
The precise relief requested, such as cancellation or reduction of specified assessments.
The taxpayer’s or authorized representative’s signature.
Proof of authority if signed or filed by a representative, such as a special power of attorney, secretary’s certificate, board authorization, or other appropriate authority.
An indexed list of attachments.

Address every issue being contested. Under RR No. 18-2013, an issue left unprotested—or challenged without its factual and legal basis—may be treated as undisputed. The tax attributable to that issue may become final and collectible, including applicable surcharge and interest.

Where and how to file

Under Revenue Memorandum Order No. 6-2023, protest letters and requests for reconsideration or reinvestigation are received by the office of the concerned Regional Director or Assistant Commissioner–Large Taxpayers Service who signed the PAN, FAN, or FLD, for referral, recording, and resolution.

Follow the receiving instructions and address stated in the assessment. Confirm the proper office if the audit has been transferred or consolidated. Do not assume that sending the protest to the revenue officer who conducted the audit, or sending an ordinary email, constitutes valid filing.

Obtain strong proof of filing:

A full copy bearing the BIR’s received stamp, date, time, and receiving officer’s details.
An official registry or authorized-courier record showing timely dispatch and delivery, if that filing method is permitted.
A complete duplicate of every exhibit actually submitted.
A signed transmittal or document inventory for later supporting documents.

File early enough to correct a rejected, incomplete, or misdirected submission before the deadline.

Build the protest around evidence

The taxpayer generally has the burden of establishing the factual basis for deductions, tax credits, exemptions, payments, and other positions asserted in the protest.

Preserve and organize:

The FLD/FAN, PAN, Letter of Authority or electronic Letter of Authority, notices, and proof of service.
Tax returns, amended returns, payment confirmations, and BIR forms.
Audited financial statements, trial balances, general ledgers, and journal entries.
Sales invoices and other valid source documents.
Withholding tax certificates and reconciliations to income reported.
Bank statements, contracts, purchase orders, delivery records, and proof of payment.
Importation, customs, excise-tax, and inventory records where relevant.
Correspondence with revenue officers and copies of every prior submission.
Corporate approvals and proof of the representative’s authority.
A chronological audit log identifying who sent, received, or discussed each document.

Prepare reconciliations that connect the source documents to the return and then to each BIR adjustment. A large folder of unexplained documents is less persuasive than an indexed, issue-specific evidentiary trail.

Check both the merits and the assessment procedure

Possible grounds depend on the records, but commonly require examination of:

Mathematical, classification, or reconciliation errors.
Tax payments or credits not recognized.
Double counting of income or disallowances.
Whether the transaction is taxable, exempt, zero-rated, deductible, or subject to the rate applied.
Whether the assessment was issued within the applicable prescriptive period and whether any waiver was valid.
Whether the audit and assessment were performed by properly authorized revenue officers and within the authority granted.
Whether required notices were validly issued and served.
Whether the PAN, FLD/FAN, and later decision adequately stated the facts and legal grounds.
Whether the FLD/FAN made a definite demand for a determinable liability.
Whether surcharge, interest, or other additions were correctly computed.
Whether factual allegations of fraud or non-filing have adequate support.

As a general rule, the BIR has three years to assess, counted from the last day prescribed for filing the return or the actual filing date, whichever is later. Important exceptions apply, including false or fraudulent returns made with intent to evade tax and failure to file a return. Waivers and special statutes can also affect the computation. Prescription must be calculated separately for each return, tax type, and period.

A procedural defect should be raised in the timely protest together with all substantive objections. Do not assume that alleging a “void assessment” permits the 30-day deadline to be ignored.

What happens after the protest

The BIR may request clarification, evaluate the existing records, conduct a reinvestigation, partially cancel the assessment, or issue a Final Decision on Disputed Assessment (FDDA).

An FDDA must state the facts and applicable law, regulations, or jurisprudence on which it is based and indicate that it is the final decision. Nevertheless, a collection letter, warrant, or similarly worded communication may create an urgent appeal issue if it shows that the BIR has finally rejected the protest. Have the substance and sequence of all post-protest notices reviewed immediately.

Denial by an authorized representative

If the Commissioner’s duly authorized representative denies the protest in whole or in part, the taxpayer has 30 days from receipt to choose one of these routes:

File a petition for review with the Court of Tax Appeals; or
Elevate the protest to the Commissioner through a request for reconsideration.

An administrative appeal to the Commissioner is limited to reconsideration. A new reinvestigation is not allowed at that stage, and only issues raised in the representative’s decision will be entertained.

Denial by the Commissioner

If the Commissioner denies the protest or administrative appeal, file the CTA appeal within 30 days from receipt. Filing another motion for reconsideration with the Commissioner does not stop or extend the 30-day CTA period.

If the BIR does not act within 180 days

For a request for reconsideration, the 180-day period is generally counted from filing the protest. For reinvestigation, it is counted from submission of the required supporting documents within the 60-day period.

After the applicable 180 days expire without action, the taxpayer has two mutually exclusive options:

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

The Supreme Court has recognized the option to await a final decision, including in Lascona Land Co. v. Commissioner of Internal Revenue and Light Rail Transit Authority v. Bureau of Internal Revenue.

Do not drift between the two routes. Once a taxpayer appeals the inaction, it cannot also treat a later BIR decision as the basis for a separate appeal. Have the 180th and 30th days independently checked before choosing.

Special note on consolidated assessments in 2026

Current BIR audit reforms use a single-instance audit and consolidation framework for certain pending audits covering the same taxpayer and taxable year.

Under RMO No. 6-2026, qualifying FAN-level consolidation requires specific safeguards. A properly issued Consolidated FAN must expressly supersede the prior FAN for consolidation purposes, and a fresh 30-day protest period runs from receipt of the Consolidated FAN.

Do not assume that every replacement, corrected, or consolidated document automatically restarts the deadline. The result depends on whether the order’s conditions were satisfied, including proper service, the status of the earlier assessment, written conformity, any required waiver, and the timing of consolidation.

Appealing to the Court of Tax Appeals

A judicial appeal is initiated by a petition for review in the appropriate CTA Division under the Revised Rules of the Court of Tax Appeals.

The petition must comply with requirements on verification, certification against forum shopping, attachments, service, docket fees, and supporting evidence. The CTA has specialized jurisdiction; filing in an ordinary trial court does not preserve a missed CTA deadline.

An appeal generally does not suspend payment, levy, distraint, or sale for collection of the tax. Under Republic Act No. 1125, as amended by Republic Act No. 9282, the CTA may suspend collection when it may jeopardize the interests of the government or taxpayer. The court may require a deposit or a surety bond of not more than twice the amount claimed, subject to recognized exceptions and the facts of the case.

CTA counsel should therefore be engaged before—not after—the 30-day appeal period is nearly over.

Common mistakes to avoid

Treating a PAN reply as the protest against the FLD/FAN.
Counting from the date the notice was forwarded to management instead of the legally relevant receipt date.
Filing only a request for an extension or copies of records.
Failing to identify reconsideration or reinvestigation.
Choosing reinvestigation without identifying the new or additional evidence.
Omitting the date of the assessment or the legal basis for the protest.
Making general objections instead of answering each finding.
Forgetting that unprotested issues may become final.
Submitting reinvestigation evidence after the 60-day period.
Filing with the wrong BIR office or relying on an unconfirmed email.
Failing to keep proof of filing and a complete copy of the submission.
Waiting indefinitely without calculating the 180-day period.
Filing another motion with the Commissioner and assuming it stops the CTA deadline.
Assuming a CTA appeal automatically stops collection.
Signing a waiver, conformity, compromise, or admission without understanding its effect on prescription or liability.

When professional help is urgent

Contact a Philippine tax lawyer immediately if:

Fewer than ten days remain before a 15-, 30-, or 60-day deadline.
The protest or CTA deadline may already have expired.
You received an FDDA, Preliminary Collection Letter, Final Notice Before Seizure, warrant of distraint or levy, garnishment notice, or notice of auction.
The BIR alleges fraud, deliberate non-filing, falsified documents, or possible criminal violations.
Bank accounts, receivables, inventory, or real property are threatened.
Multiple FANs or a Consolidated FAN were issued.
The assessment involves a disputed waiver, prescription, service, or Letter of Authority.
The amount is material to the taxpayer’s operations.
The case must be elevated to the Commissioner or the CTA.

Frequently asked questions

Must I pay the assessment before filing a protest?

Generally, no. Section 228 does not impose a pay-first requirement for a timely administrative protest against an FLD/FAN. Undisputed portions, however, can become final and collectible, and a later CTA appeal does not automatically suspend collection.

Can I ask for more than 30 days to protest?

Do not rely on an extension. The 30-day protest period is statutory and strictly applied. The BIR occasionally issues official, limited extensions after disasters or government suspensions, but an extension applies only if the taxpayer, place, document, and deadline fall squarely within that issuance.

Can I file the protest by email?

Use email only when an applicable official issuance or the assessment’s instructions clearly authorize it, and obtain confirmation of valid receipt. Ordinary email to a revenue officer is not a safe substitute for filing with the proper receiving office.

What if I received only a collection letter and never saw the FLD/FAN?

Act immediately. Obtain the assessment docket, proof of service, and copies of every notice. Defective service may be material, but actual receipt by authorized personnel or at a registered or known address can defeat an assumption that no valid service occurred.

What if I missed the 30-day protest deadline?

The general consequence is that the assessment becomes final, executory, and demandable. Potential objections involving service, prescription, authority, or a legally void assessment are highly fact-dependent and do not justify further delay. Seek counsel before responding to collection.

May I wait beyond 180 days for the BIR’s decision?

Yes, current law and jurisprudence recognize that option. If you wait, appeal the eventual final decision within 30 days from receipt. Alternatively, appeal the inaction within the specific 30-day window after the 180-day period. The two routes are mutually exclusive.

Does filing with the CTA stop BIR collection?

No. A separate request for suspension may be necessary, and the CTA may impose a deposit or bond requirement.

Official and primary references

This article provides general legal information, not legal or tax advice for a specific assessment. Deadlines and available arguments depend on the actual notices, proof of receipt, audit record, and later BIR actions. Sources were checked as of August 3, 2026.