Quick answer

If you receive a BIR Formal Letter of Demand and Final Assessment Notice (FLD/FAN), file a valid written administrative protest within 30 days from receipt. Choose either:

Request for reconsideration — asks the BIR to reevaluate the assessment using records already available; or
Request for reinvestigation — relies on newly discovered or additional evidence, which must be submitted within 60 days from filing the protest.

File with the duly authorized BIR official who signed the FLD/FAN. Address every disputed tax, period, factual finding, and legal issue. A vague objection, request for more time, or statement that documents are still being compiled may not qualify as a valid protest.

After a valid protest, the BIR generally has 180 days to act. Depending on who issued the denial and whether the BIR acted at all, the taxpayer may appeal administratively to the Commissioner of Internal Revenue or judicially to the Court of Tax Appeals (CTA). Most appeal periods are only 30 days and missing them can make the assessment final, executory, and demandable.

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

Identify the document you received

Different BIR notices trigger different responses:

Document	What it generally means	Usual response period
Notice for Informal Conference or Notice of Discrepancy	The audit findings are still being discussed before assessment	Act promptly; the informal-conference stage cannot ordinarily extend beyond 30 days from receipt
Preliminary Assessment Notice (PAN)	The BIR proposes a deficiency assessment	Respond within 15 days from receipt
FLD/FAN	A formal assessment and demand for payment has been issued	File a valid protest within 30 days from receipt
Final Decision on Disputed Assessment (FDDA)	The BIR has decided the protest	Usually appeal within 30 days from receipt
Collection Letter, Final Notice Before Seizure, or Warrant of Distraint and/or Levy	The BIR is pursuing collection	Obtain legal help immediately; the correct remedy and deadline depend on the record

The PAN response is important, but it is not a substitute for the protest against the FLD/FAN. Even if you answered the PAN, you must still file a proper protest within 30 days after receiving the FLD/FAN.

Revenue Regulations No. 7-2018 governs the current informal-conference stage, while RR No. 18-2013 governs the PAN, FLD/FAN, protest, FDDA, and modes of service.

Record the date and manner of receipt

The protest period normally runs from actual, legally effective receipt of the FLD/FAN—not simply from the date printed on it. Immediately preserve:

The original envelope, registry notice, courier pouch, and tracking record;
The receiving copy showing the recipient’s name, position, signature, date, and time;
Security logs, mailroom records, CCTV, and internal document-routing records;
Any power of attorney or tax-agent appointment; and
Proof of the company’s registered BIR address and any properly filed address updates.

BIR notices may be served personally, by substituted service, or by mail under RR No. 18-2013. Service on a duly appointed tax agent may count as service on the taxpayer. Recent Supreme Court decisions emphasize that proper service is part of tax-assessment due process, particularly where a notice is left with someone whose authority or relationship to the taxpayer is not established. See Mannasoft Technology Corporation v. CIR and CIR v. Fort 1 Global City Center, Inc..

Day 1 is ordinarily the day after receipt. Nevertheless, do not make casual assumptions about weekends, holidays, office closures, or local disaster extensions. An extension applies only when supported by the governing law, court rule, or a BIR issuance that actually covers the taxpayer, document, and deadline.

Check whether the assessment followed due process

Review the entire audit file, not just the total amount. Relevant questions include:

Was the assessment issued and signed by an authorized BIR official?
Does each assessment state the factual and legal basis? Section 228 requires the taxpayer to be informed in writing of the law and facts on which the assessment is based. A spreadsheet of amounts, unexplained conclusion, or generic citation may be inadequate, although validity ultimately depends on the complete FLD/FAN and its attachments.
Was a PAN properly issued and served? A PAN is generally required. The Tax Code permits an FLD/FAN to be issued without a PAN only when:
- The deficiency results from a mathematical error apparent on the face of the return;
- Tax withheld differs from the amount actually remitted;
- An amount claimed as a refund or tax credit for excess creditable withholding tax was also carried over to the succeeding taxable year;
- Excise tax on excisable articles was not paid; or
- An article acquired tax-free by an exempt person was transferred to a non-exempt person.
Was there a real opportunity to answer the PAN before the FLD/FAN was issued?
Was the correct taxpayer, tax type, and taxable period assessed?
Was the assessment issued within the applicable limitation period? The general period is three years, calculated under Section 203 of the Tax Code. Different rules may apply to a false or fraudulent return made with intent to evade tax, failure to file a return, or a valid written waiver extending the assessment period. These issues require close review of return-filing dates, waivers, notices, and proof of service.
Did the audit stay within a valid Letter of Authority? Preserve the Letter of Authority and any reassignment, memorandum of assignment, or other audit authorization. The consequences of a defect depend on the exact document and controlling jurisprudence.

Raise procedural and substantive defenses in the timely protest. Do not simply ignore an FLD/FAN because you believe it is void. Filing a protective, complete protest avoids making the case depend entirely on a disputed service or validity argument.

Choose the correct kind of protest

Request for reconsideration

Use reconsideration when the assessment can be resolved using records already available to the BIR. It may involve factual questions, legal questions, or both.

Examples include:

The BIR misapplied a tax rate or statute;
The assessment duplicates an item already assessed;
The BIR overlooked a return, schedule, or document already submitted;
The computation contains an error; or
The assessment is allegedly prescribed or procedurally invalid.

Under RR No. 18-2013, the special 60-day supporting-document period does not apply to a request for reconsideration. The BIR’s 180-day period is generally counted from the filing of the protest.

Request for reinvestigation

Use reinvestigation when you intend to present newly discovered or additional evidence not already in the audit record. The protest must identify the additional evidence you intend to submit.

All relevant supporting documents must be submitted within 60 days from filing the protest. The BIR’s 180-day period is then generally counted from the submission of those documents.

A request for reinvestigation that is granted may also affect the limitation period for collection. This is one reason the choice should reflect the actual evidence and strategy rather than merely the label preferred by the taxpayer.

The two remedies are alternatives. Do not ambiguously ask for both. Under BIR procedures, an unclear protest may be treated as a request for reconsideration.

What the protest letter should contain

At minimum, prepare a signed protest containing:

The taxpayer’s complete registered name, TIN, address, and contact information;
The assessment number, taxable period, tax types, date of the FLD/FAN, and date and manner of receipt;
An express statement that the taxpayer is filing a request for reconsideration or request for reinvestigation;
For reinvestigation, a specific description of the new or additional evidence to be presented;
A separate discussion of every disputed assessment item;
The material facts supporting the taxpayer’s position;
The applicable statutes, regulations, and jurisprudence;
A corrected computation, where relevant;
The precise relief requested, such as cancellation or reduction of particular assessment items;
A schedule distinguishing disputed and undisputed amounts;
An indexed list of attachments; and
Proof that the signatory or representative is authorized to act for the taxpayer.

If several issues appear in the FLD/FAN, discuss each one. An issue that is not disputed, or for which the protest states no factual and legal basis, may be treated as undisputed. The related amount can become final and collectible even while other issues remain under protest.

The Supreme Court held in CIR v. Citysuper, Inc. that a letter merely saying the taxpayer was compiling documents did not satisfy the requirements for a valid protest. There was consequently no disputed assessment over which the CTA could exercise appellate jurisdiction.

Where and how to file

File the PAN response or FLD/FAN protest with the duly authorized representative of the Commissioner who signed the relevant notice. Revenue Memorandum Circular No. 11-2014 identifies this as the proper receiving office. An administrative appeal from that official’s adverse decision is filed with the Office of the Commissioner.

Before filing:

Confirm the receiving office shown in the FLD/FAN.
Prepare the required number of copies and authority documents.
Obtain a date-stamped receiving copy bearing the office, recipient, and time of filing.
If filing through an authorized mode other than personal delivery, retain complete proof of dispatch and receipt.
Do not assume that an ordinary email, online inquiry, or submission to an unrelated RDO constitutes filing. Use an electronic channel only if a current BIR issuance and the proper receiving office expressly authorize it for the case.

For a reinvestigation, submit the evidence with an indexed transmittal letter within 60 days. Obtain separate proof of submission identifying every document delivered. If the BIR examines original records, preserve a written record of what was presented, when, where, and to whom.

What happens after filing

Maintain a deadline sheet showing:

Receipt date of the FLD/FAN;
Protest filing date;
Supporting-document deadline, if reinvestigation was requested;
Actual date the supporting documents were submitted;
End of the applicable 180-day period;
Receipt date of every decision or collection notice; and
The corresponding 30-day appeal deadline.

The BIR should decide the protest through an FDDA stating the facts and applicable law, regulations, or jurisprudence and identifying itself as the final decision. A letter’s legal effect depends on its substance and the surrounding record, not only its title. Treat any communication that denies the protest, demands payment, or begins collection as urgent.

If the protest is denied

Denial by the Commissioner’s authorized representative

Within 30 days from receipt, choose one of these remedies:

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

An administrative appeal to the Commissioner cannot be a new request for reinvestigation. The appeal is limited to the issues covered by the authorized representative’s decision.

Denial by the Commissioner

File a petition for review with the CTA within 30 days from receipt.

A motion asking the Commissioner to reconsider the Commissioner’s own denial does not suspend or restart the 30-day period for going to the CTA.

If the BIR does not act within 180 days

After the applicable 180-day period expires, the taxpayer has two mutually exclusive choices:

Appeal the BIR’s inaction to the CTA within the next 30 days; or
Wait for the final BIR decision, then appeal that decision to the CTA within 30 days from receipt.

Choosing to appeal the inaction bars the taxpayer from later treating the eventual administrative decision as the alternative route. Conversely, a taxpayer who waits must be prepared to appeal promptly when a final decision arrives.

The Supreme Court confirmed these alternatives in Lascona Land Co., Inc. v. CIR. The exact starting point for the 180 days must be documented carefully: under RR No. 18-2013, it is generally the protest-filing date for reconsideration and the supporting-document submission date for reinvestigation.

Appealing to the Court of Tax Appeals

A CTA appeal is commenced by a petition for review before a CTA Division under Republic Act No. 1125, as amended by Republic Act No. 9282 and the Revised Rules of the Court of Tax Appeals.

The petition must satisfy the CTA’s requirements on verification, allegations, attachments, service, copies, and docket and other lawful fees. Do not assume that a request for an extension will be granted or that an administrative follow-up suspends the statutory period.

An appeal to the CTA does not automatically stop collection. The CTA may suspend collection when the statutory conditions are met and may require a deposit or surety bond of not more than twice the amount claimed. If collection is imminent, counsel should assess whether to request suspension under Rule 10 of the CTA Rules.

There is no minimum assessment amount for invoking the CTA’s appellate jurisdiction over a properly disputed BIR assessment. The practical cost of litigation may nevertheless influence whether judicial appeal, payment, or an authorized compromise route is appropriate.

Evidence to preserve

Keep an organized physical and electronic case file containing:

Tax returns, amended returns, and filing confirmations;
Financial statements, trial balances, ledgers, journals, and reconciliations;
Invoices, receipts, withholding certificates, contracts, and delivery records;
Bank statements and proof of tax payments;
The Letter of Authority and all audit requests;
Notice of Discrepancy, PAN, FLD/FAN, FDDA, and collection notices;
Envelopes, registry receipts, courier records, and proof of service;
Every submission to the BIR, including attachment inventories;
Date-stamped receiving copies and electronic acknowledgments;
Minutes or notes of conferences with revenue officers;
Corporate secretary’s certificates, board resolutions, special powers of attorney, and tax-agent appointments; and
A written chronology of every relevant event.

Retain originals whenever possible. Work from scanned copies and keep secure backups with stable filenames.

Common mistakes

Treating the PAN response as the protest against the FLD/FAN;
Counting from the document date while ignoring the provable receipt date;
Filing only a request for an extension or a generic statement of disagreement;
Failing to identify whether the protest is reconsideration or reinvestigation;
Omitting the factual and legal basis for one of several assessment issues;
Failing to submit reinvestigation evidence within 60 days;
Filing with the wrong BIR office without obtaining proof that it reached the proper official;
Assuming an email or verbal discussion constitutes a filed protest;
Waiting for another letter after receiving an FDDA or clear final denial;
Filing another motion with the Commissioner and assuming it tolls the CTA deadline;
Ignoring an assessment because service or due process appears defective;
Assuming that a CTA appeal automatically stops collection; and
Losing envelopes, receiving logs, or proof of filing that establish the controlling dates.

When legal help is urgent

Consult a Philippine tax lawyer immediately when:

Fewer than 10 days remain before a protest or appeal deadline;
An FDDA, collection letter, Final Notice Before Seizure, garnishment notice, or warrant of distraint or levy has been received;
The BIR is contacting banks, customers, tenants, or other third parties about collection;
The assessment involves alleged fraud, false returns, unreported sales, fictitious transactions, or possible criminal referral;
The BIR disputes whether the protest was valid or timely;
Service was made at an old address or on an unauthorized person;
The assessment is material to the taxpayer’s operations or ability to continue business;
A waiver, prescription issue, or defective Letter of Authority is involved; or
The taxpayer is considering a CTA appeal or an application to suspend collection.

A CPA can help reconstruct accounts and computations, but legal issues involving jurisdiction, finality, service, prescription, and CTA procedure should be handled with a Philippine lawyer experienced in tax litigation.

Frequently asked questions

Can I protest a PAN?

You may and generally should answer a PAN within 15 days, but the statutory administrative protest is filed against the later FLD/FAN. If the BIR never issues an FLD/FAN, there ordinarily is no final assessment to protest under Section 228.

Is a PAN always required?

No. Section 228 lists five specific exceptions, including facial mathematical errors and discrepancies between taxes withheld and remitted. Outside an applicable exception, failure to issue and properly serve the PAN may invalidate the assessment.

Must I pay the disputed amount before filing a BIR protest?

Generally, no. A valid administrative protest does not require advance payment of the genuinely disputed portion. Undisputed assessment items, however, become final and should be addressed separately.

What if I agree with only part of the assessment?

Identify and pay or arrange payment of the accepted portion, while expressly protesting each remaining issue. Attach a schedule showing how the disputed and undisputed amounts were computed.

Can the BIR accept a late protest?

Once the 30-day period expires without a valid protest, the assessment generally becomes final, executory, and demandable. Do not rely on informal assurances that a late letter will be considered.

What if the BIR is silent after I submit my protest?

Track the 180-day period. When it expires, either appeal the inaction to the CTA within 30 days or wait for a final decision and appeal within 30 days from receiving it. Obtain advice before choosing because the remedies are mutually exclusive.

Does a collection notice automatically mean I lost the protest?

Not always. A collection notice may raise questions about whether the assessment became final, whether the BIR denied the protest, or whether collection began prematurely. Because the notice may trigger a separate judicial deadline or immediate enforcement, have the complete record reviewed at once.

Can I protest without a lawyer?

An individual taxpayer may prepare an administrative protest, but the formal requirements and short deadlines leave little room for correction. A corporation should also ensure that the signatory and representative are properly authorized. CTA litigation should be handled by qualified counsel.

Official references

This article provides general legal information, not legal or tax advice for a particular assessment. Deadlines and remedies depend on the documents, date and manner of receipt, issuing official, and procedural history. Sources and procedures were checked as of August 3, 2026.