Quick answer

You may contest a BIR deficiency assessment by filing a valid written protest against the Formal Letter of Demand and Final Assessment Notice (FLD/FAN) within 30 days from receipt. The protest must identify whether you seek reconsideration or reinvestigation, specify the assessment date, and state the factual and legal grounds for disputing each assessment item. A placeholder letter saying only that documents are still being gathered is not enough.

If you request reinvestigation, submit all relevant supporting documents within 60 days from filing the protest. If the BIR denies the protest—or does not act within the applicable 180-day period—the dispute may be taken to the Court of Tax Appeals (CTA), generally within another 30-day period.

These deadlines are strict. Record the exact receipt date of every BIR notice, preserve proof of filing, and obtain professional help before the deadline—not after it.

Know which document you received

BIR audits normally pass through several stages:

Document or stage	What it means	Immediate action
Notice of Discrepancy (NoD)	Preliminary audit findings and an opportunity to explain discrepancies	Attend the scheduled discussion and submit supporting records promptly
Preliminary Assessment Notice (PAN)	Proposed deficiency assessment	Respond within 15 days from receipt
FLD/FAN	Formal assessment and demand for payment	File a valid administrative protest within 30 days from receipt
Final Decision on Disputed Assessment (FDDA) or equivalent final denial	Decision on the protest	Choose the proper administrative or CTA remedy within 30 days from receipt
Collection notice, warrant, garnishment, levy or seizure notice	BIR may be treating the assessment as final and collectible	Obtain tax counsel immediately

The NoD procedure is intended to let taxpayers explain audit discrepancies before an assessment is issued. The BIR’s prescribed NoD format is found in Revenue Memorandum Circular No. 102-2020.

A response to the NoD or PAN does not replace the protest required after receipt of an FLD/FAN. Even if you already gave the examiner a detailed explanation, file a separate, compliant protest against the FLD/FAN.

When the BIR may skip the PAN

Section 228 of the National Internal Revenue Code permits an FLD/FAN to be issued without a PAN when the assessment results from:

A mathematical error appearing on the face of the return;
A discrepancy between tax withheld and tax actually remitted;
Carrying over excess creditable withholding tax that was also claimed for refund or tax credit;
Unpaid excise tax on excisable articles; or
The sale, transfer or disposition to a non-exempt person of an article acquired by an exempt person.

Outside these statutory exceptions, failure to give the taxpayer the required pre-assessment opportunity may be a due-process issue. The assessment must also inform the taxpayer in writing of its factual and legal bases; otherwise, Section 228 provides that it is void. The Supreme Court has repeatedly enforced these requirements, including in Commissioner of Internal Revenue v. Avon Products Manufacturing, Inc..

The deadlines that control the protest

The governing deadlines under Revenue Regulations No. 18-2013 are:

Thirty days from receipt of the FLD/FAN: File the written protest.
Sixty days from filing the protest: If requesting reinvestigation, submit all relevant supporting documents.
One hundred eighty days for BIR action:
- For reconsideration, count from filing of the protest.
- For reinvestigation, count from submission of the required supporting documents within the 60-day period.
Thirty days after denial: Use the proper administrative appeal or file a petition for review with the CTA.
Thirty days after the 180-day period expires: If choosing to appeal the BIR’s inaction, file with the CTA within this window.

Do not assume that a meeting, follow-up letter, pending document request, informal assurance or motion for reconsideration will extend a statutory deadline. Calculate each date conservatively and confirm it against the actual notices and proof of receipt.

Choose the correct kind of protest

Request for reconsideration

Choose reconsideration when you want the BIR to re-evaluate the assessment using the records already available. It may involve factual questions, legal questions or both, but it does not depend on newly discovered or additional evidence.

The special 60-day document-submission period does not apply to reconsideration. You may still attach copies of existing records to organize and explain your position.

The 180-day period for BIR action is counted from the filing of the protest.

Request for reinvestigation

Choose reinvestigation when you intend to present newly discovered or additional evidence. The protest must identify the additional evidence you plan to submit.

All relevant supporting documents must be submitted within 60 days from filing the protest. The regulations describe these as the documents the taxpayer considers necessary to support the legal and factual bases of the dispute.

The 180-day period is counted from submission of the required documents. Your final transmittal should therefore state clearly that it completes your supporting-document submission and should carry reliable proof of its filing date.

Choosing between the two remedies affects both the evidence the BIR may consider and the date from which the 180-day period runs. Do not select reinvestigation merely to gain time.

What a valid protest should contain

There is no substitute for a complete, issue-by-issue protest. At minimum, include:

The taxpayer’s complete name, TIN, registered address and contact information;
The FLD/FAN number, assessment numbers, assessment date and date of receipt;
The taxable period, tax types and amounts involved;
An express statement that the letter is a request for reconsideration or request for reinvestigation;
For reinvestigation, a description of the newly discovered or additional evidence to be presented;
A separate discussion of every disputed finding;
The material facts supporting the taxpayer’s position;
The applicable statutes, regulations and jurisprudence supporting each ground;
Corrected computations, reconciliations and schedules where appropriate;
A specific request to cancel, withdraw or reduce the disputed assessment;
A list of attachments; and
The taxpayer’s signature or the signature and authority documents of its authorized representative.

Do not rely on broad statements such as “the assessment is excessive,” “we disagree,” or “supporting documents will follow.” In Commissioner of Internal Revenue v. Citysuper, Inc., the Supreme Court treated a letter as an invalid protest because it failed to comply with the required form and content. A defective protest may leave the CTA without a disputed assessment to review.

If several issues are assessed, address every issue individually. An item not disputed with supporting facts and legal grounds may be treated as undisputed, final and demandable. The regulations require payment of the tax attributable to undisputed issues, including applicable additions.

Where and how to file

File the protest with the office of the Commissioner’s duly authorized representative who signed the FLD/FAN. Depending on the taxpayer and issuing office, this may be the concerned Revenue Region or Large Taxpayers office. Current BIR audit procedures direct protest correspondence to the office of the concerned Regional Director or Assistant Commissioner–Large Taxpayers Service who signed the assessment; see Revenue Memorandum Order No. 6-2023.

Before filing, confirm the receiving office from the FLD/FAN and current official BIR instructions. Do not leave the only copy with the examiner or send it to a general email address unless an applicable BIR issuance or written instruction expressly authorizes that channel.

For personal filing:

Bring enough signed copies for the BIR and the taxpayer;
Have the taxpayer’s copy stamped “received” with the date, office and receiving officer;
Obtain any control, docket or reference number issued; and
Check that the receiving stamp appears on the protest itself and not only on a detachable cover sheet.

If another officially accepted filing method is used, retain proof showing the complete document, destination and date of transmission or delivery. Filing in the wrong office can render a protest ineffective.

Review both the merits and the assessment process

A protest should challenge the assessment’s substance and any applicable procedural defects. Possible issues include:

Factual and computational errors

Compare the BIR schedules with the taxpayer’s returns, audited financial statements, ledgers, withholding certificates, invoices, receipts, bank records and third-party information. Look for duplicated entries, timing differences, incorrect tax bases, unreconciled beginning balances and amounts already declared or paid.

Incorrect legal treatment

Determine whether the BIR applied the correct tax provision, rate, exemption, deduction, withholding rule, sourcing rule and taxable period. Separate disputes over the basic tax from disputes over surcharge, interest and compromise penalties.

Inadequate factual or legal basis

The PAN, FLD/FAN and FDDA must sufficiently state the facts and law supporting the assessment or decision. A table of amounts without an adequate explanation may not satisfy due process. Whether attachments and prior written communications cure a particular deficiency depends on the complete record.

Improper or premature service

Check where, when and on whom each notice was served. Under RR No. 18-2013, BIR notices may be served personally, by permitted substituted service, or by mail or professional courier. Service on an appointed tax agent may be treated as service on the taxpayer.

Preserve envelopes, registry records, courier tracking and affidavits from the people who received—or allegedly received—the documents. The Supreme Court has treated proper service as part of assessment due process, as discussed in South Entertainment Gallery, Inc. v. Commissioner of Internal Revenue.

Lack of audit authority

Review the Letter of Authority and the identities of the officers who actually examined the books. The Supreme Court has ruled that reassignment to an officer not covered by a proper new or amended authority can invalidate the resulting assessment. See Commissioner of Internal Revenue v. McDonald’s Philippines Realty Corp..

Prescription

As a general rule, the BIR must assess within three years from the statutory return-filing date or the actual filing date, whichever is later. Different rules can apply to late, false or fraudulent returns, failure to file, valid waiver agreements and other statutory exceptions. Prescription must be calculated separately for each tax and period using the actual returns, assessment dates and waiver documents.

Even if you believe an assessment is void or prescribed, file a timely protest. Do not rely on a procedural objection as a reason to miss the 30-day deadline.

What happens after the protest

The BIR may grant the protest, deny it entirely or reduce only part of the assessment. Its formal decision should state the facts and applicable law and identify itself as the final decision.

If the denial is issued by the Commissioner’s duly authorized representative, the taxpayer generally has two alternatives within 30 days from receipt:

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 is limited to reconsideration; reinvestigation is not allowed at that stage. If the Commissioner denies the protest or administrative appeal, file the CTA petition within 30 days from receipt. A further motion asking the Commissioner to reconsider that denial does not suspend the CTA deadline.

Read every adverse communication by its substance, not merely its title. A collection letter or final notice may be treated as the decision on the protest if its wording and context show that the BIR has finally rejected the taxpayer’s position. Later requests to reopen the case may not restart the appeal period.

If the BIR does nothing for 180 days

When the applicable 180-day period expires without a decision, the taxpayer has two mutually exclusive choices:

Appeal the inaction: File a petition for review with the CTA within 30 days after the 180-day period expires; or
Wait for a final BIR decision: Once that decision is received, appeal it to the CTA within 30 days.

The Supreme Court confirmed these options in Lascona Land Co., Inc. v. Commissioner of Internal Revenue. Once the taxpayer chooses to appeal the inaction, that choice bars the alternative of continuing to wait for an administrative decision.

Waiting may avoid immediate litigation, but it can prolong uncertainty and increase exposure to continuing interest or collection measures. The decision should be made with counsel after reviewing the assessment amount, strength of evidence, cash-flow consequences and any signs that collection action is beginning.

Taking the case to the CTA

An appeal from the Commissioner’s decision or qualifying inaction is filed through a petition for review with a CTA Division. The governing 30-day period comes from Section 228, Republic Act No. 1125 as amended by Republic Act No. 9282, and the Revised Rules of the Court of Tax Appeals.

CTA litigation involves jurisdictional deadlines, verification, certification against forum shopping, supporting records, proof of authority, service requirements, docket fees and current electronic-submission rules. Engage a tax litigator early enough to prepare the petition and evidence before the 30-day period expires.

An appeal does not automatically stop collection. The CTA may suspend collection when the statutory conditions are met, usually upon a properly supported motion and subject to such deposit or surety bond as the court may require, within the limits fixed by law.

Evidence to preserve now

Create one secured assessment file containing:

The Letter of Authority and any replacement or reassignment authority;
The NoD, PAN, FLD/FAN, FDDA and every attachment;
Original envelopes, registry notices and courier packaging;
Proof of each receipt and filing date;
Copies of all responses, protests and document transmittals;
BIR receiving stamps, control numbers and delivery records;
Meeting invitations, attendance records and contemporaneous notes;
Tax returns, proof of filing and proof of payment;
Books, ledgers, invoices, receipts and withholding certificates;
Contracts, bank records and third-party confirmations relevant to the findings;
Reconciliation schedules and the source files used to prepare them;
Special powers of attorney, board resolutions and other signatory authority; and
A deadline calendar showing who is responsible for every filing.

Keep exact copies of what was submitted. A later dispute may turn on whether a particular document was included, when the submission became complete, or whether the receiving office was correct.

Common mistakes

Treating a PAN response as the protest against the FLD/FAN;
Filing a placeholder protest with no factual or legal grounds;
Failing to identify reconsideration or reinvestigation expressly;
Choosing reinvestigation but not identifying and submitting additional evidence within 60 days;
Discussing only the largest assessment item and leaving smaller items undisputed;
Filing with the examiner or wrong BIR office;
Keeping no received-stamped copy or reliable filing proof;
Counting the 180 days from the wrong event;
Assuming BIR silence means the assessment has been cancelled;
Assuming a follow-up request or motion restarts the CTA deadline;
Ignoring notices delivered to the registered address or appointed tax agent; and
Waiting for collection action before consulting counsel.

When professional help is urgent

Consult a Philippine tax lawyer, supported where appropriate by a CPA, immediately if:

The FLD/FAN protest deadline is less than ten days away;
An FDDA, final demand, warrant of distraint or levy, garnishment notice or seizure notice has been received;
The BIR alleges fraud, deliberate underdeclaration, fictitious transactions or failure to remit withholding taxes;
Criminal referral or prosecution is mentioned;
The assessment threatens payroll, banking facilities, permits or business continuity;
Receipt or service of an assessment is disputed;
The audit was conducted by officers not named in the Letter of Authority;
Waivers of the assessment period were signed;
The assessment covers multiple years, related parties or cross-border transactions; or
The 180-day period has expired and a decision must be made between appealing inaction and waiting.

Frequently asked questions

Must I pay the entire assessment before protesting?

Generally, no prepayment is required to file a valid administrative protest or CTA petition. Amounts attributable to issues you do not dispute, however, become final and must be paid. Interest exposure may continue on unpaid liabilities.

Can I ask the BIR to extend the 30-day protest deadline?

Do not rely on an extension. The 30-day protest period is mandatory, and failure to file a valid protest ordinarily makes the assessment final, executory and demandable.

Can I submit evidence after the 60-day reinvestigation period?

Late additional evidence may be excluded, and the assessment may become final as to matters requiring that evidence. Submit a complete, indexed package within the period and preserve proof of submission.

What if the FLD/FAN is obviously wrong or void?

Raise the defect in a timely protest anyway. A belief that the assessment is invalid does not safely excuse inaction, and missing the protest deadline may prevent merits review.

Does B DoesIR silence after 180 days cancel the assessment?

No. It creates a choice between appealing the inaction within the next 30 days and waiting for a final decision. Silence is not an automatic cancellation.

Can I protest by email?

Only rely on email or another electronic channel when a current BIR issuance or written instruction expressly authorizes it for that filing and office. Otherwise, use the designated receiving office and obtain formal proof of timely receipt.

What if I already paid the assessment?

Payment may give rise to a separate claim for refund or tax credit, subject to different administrative and judicial deadlines. Obtain advice promptly because payment does not preserve refund rights indefinitely.

Will a CTA appeal stop garnishment or levy?

Not automatically. A separate, evidence-supported request to suspend collection may be necessary.

Official legal references

This article provides general legal information, not legal or tax advice for a particular assessment. The correct remedy may depend on the complete notices, proof of service, audit authority, tax records and prior filings. Official sources and procedures were checked through 4 August 2026.