Quick answer

If you received 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 — the BIR re-evaluates the assessment using the records already available; or
Request for reinvestigation — you will present newly discovered or additional evidence. Submit all relevant supporting documents within 60 days from filing the protest.

Address every assessment issue you dispute, state the facts and legal basis for each, identify the assessment date, and clearly name the remedy chosen. A letter that merely says you disagree or are still gathering documents may be treated as an invalid protest. If no valid protest is filed on time, the assessment generally becomes final, executory, and demandable.

A Preliminary Assessment Notice (PAN) is different: respond to it within 15 days from receipt, but the formal 30-day protest is directed against the later FLD/FAN. The governing rules are Section 228 of the National Internal Revenue Code and Revenue Regulations No. 18-2013.

First identify the document you received

The correct response depends on the document—not simply on whether it contains the word “assessment.”

Notice of Discrepancy or informal-conference notice

This is generally an early audit stage. Respond by the date stated and attend the discussion with organized records and written explanations. Under current BIR audit policy, unresolved issues after the discussion may proceed to assessment. An informal conference generally may not extend beyond 30 days from receipt of its notice under Revenue Regulations No. 7-2018.

This is an opportunity to resolve factual errors early, but it is not a substitute for protesting a later FLD/FAN.

Preliminary Assessment Notice

A PAN contains proposed findings. File a written response within 15 days from receipt. Explain the factual and legal errors and attach supporting records that are already available.

The PAN is ordinarily required before an FLD/FAN, but Section 228 allows an FLD/FAN to be issued without a PAN when the deficiency results from:

A mathematical error apparent on the face of the return;
A discrepancy between tax withheld and tax remitted;
Carrying over an excess creditable withholding tax amount that was also claimed for refund or tax credit;
Unpaid excise tax on excisable articles; or
Transfer of certain tax-exempt purchases or imports to non-exempt persons.

If no exception applies and the BIR skipped the PAN, that may be a due-process ground against the assessment. The effect depends on the complete record and should be evaluated by tax counsel.

Formal Letter of Demand and Final Assessment Notice

The FLD/FAN fixes and demands payment of the alleged deficiency. This is the document that must ordinarily be protested within 30 days from receipt.

Replying to the PAN does not preserve your rights against the FLD/FAN. You must file a separate, valid protest even if the FLD/FAN repeats the PAN findings. The Supreme Court confirmed this distinction in Commissioner of Internal Revenue v. Court of Tax Appeals, G.R. No. 261065.

Final Decision on Disputed Assessment

An FDDA is the BIR’s decision on your protest. A denial signed by the Commissioner’s authorized representative may generally be:

Appealed directly to the Court of Tax Appeals within 30 days from receipt; or
Elevated through a request for reconsideration to the Commissioner within the same 30-day period.

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

If the denial is issued by the Commissioner, appeal to the CTA within 30 days from receipt. Filing another motion for reconsideration with the Commissioner does not stop or extend the CTA deadline.

Collection letter, final demand, warrant, levy, or garnishment

Treat these as urgent. In some circumstances, a demand or collection letter that clearly communicates the BIR’s final position can be considered an appealable decision. Its legal effect depends on its language and the earlier notices. Do not wait for a document formally titled “FDDA” without having the record reviewed.

The critical deadlines

Event	General rule
Receipt of PAN	Respond within 15 days
Receipt of FLD/FAN	File a valid protest within 30 days
Reinvestigation protest filed	Submit all relevant supporting documents within 60 days from filing
Reconsideration pending before authorized representative	BIR’s 180-day period is counted from filing of the protest
Reinvestigation pending before authorized representative	The 180-day period is counted from submission of the required documents within the 60-day period
FDDA from authorized representative	Appeal to the CTA or elevate to the Commissioner within 30 days from receipt
Denial by the Commissioner	Appeal to the CTA within 30 days from receipt
Commissioner’s inaction on an administrative appeal	The 180-day period is generally counted from filing of the administrative appeal
Appeal against an FDDA filed with the Commissioner or CTA	Furnish the designated BIR office a copy within 5 days from filing

The five-day copy requirement comes from Revenue Memorandum Circular No. 43-2023. For regional cases, the copy goes to the Chief of the Assessment Division. For specified Large Taxpayers Service or National Investigation Division cases, it goes to the concerned Head Revenue Executive Assistant.

Record the exact date, time, place, and manner of receipt of every notice. Do not calculate from the notice’s printed date if it was received later. Conversely, do not assume that refusing or ignoring delivery prevents receipt: BIR rules permit personal, substituted, mail, and courier service, and service on a duly appointed tax agent may be treated as service on the taxpayer.

As of August 3, 2026, RMC No. 35-2026 provides a narrow exception during the BIR’s current energy-conservation work arrangement: when a National Office request for reconsideration of an FDDA falls due on a Friday, filing moves to the next business day when personnel are working onsite. Do not apply this exception to other filings or offices without confirming that the issuance remains applicable.

Reconsideration or reinvestigation?

Choose reconsideration when

The necessary documents are already in the BIR’s records;
The dispute primarily concerns interpretation of law, tax treatment, prescription, authority, or computation; or
No new or additional evidence is needed.

The 60-day supporting-document period does not apply to reconsideration. Nevertheless, the protest should identify and, where appropriate, reproduce the existing evidence relied upon.

Choose reinvestigation when

Important invoices, contracts, reconciliations, certificates, or third-party records were not previously considered;
Newly discovered or additional evidence is needed to correct the findings; or
The BIR’s factual assumptions cannot be answered adequately from the existing audit record.

Name the additional evidence you intend to submit. Deliver all relevant documents within 60 days from filing the protest and obtain proof of receipt. Missing this period bars the taxpayer from disputing the assessment through newly discovered or additional evidence and ordinarily leads to denial through an FDDA.

The choice can also affect prescription and later litigation. Do not label the protest casually.

What a valid protest should contain

A complete protest should ordinarily include:

Taxpayer details. State the registered name, TIN, registered address, contact information, and, for an entity, the authorized representative.
Assessment identification. Identify the FLD/FAN, assessment numbers, tax types, taxable periods, assessment date, date and manner of receipt, and amounts assessed.
Express choice of remedy. State clearly that the protest is a “request for reconsideration” or a “request for reinvestigation.” For reinvestigation, specify the new or additional evidence to be presented.
Issue-by-issue response. Address every adjustment, tax type, period, surcharge, interest item, and penalty being disputed. State the relevant facts and applicable statute, regulation, treaty provision, ruling, or jurisprudence.
Supporting computation. Reconcile the BIR’s figures with the return, books, withholding certificates, payments, and your proposed corrected amount.
Requested relief. Ask that the disputed assessment be cancelled or reduced to a specified amount, as supported by the record.
Document schedule. List and label every attachment. For reinvestigation, identify documents to follow within the 60-day period.
Authority and signature. The taxpayer or properly authorized representative should sign. Attach the applicable authorization, such as a special power of attorney, board authority, or other proof of representation.

A generic reservation letter is dangerous. In CIR v. Court of Tax Appeals, G.R. No. 239464, a letter stating that the taxpayer was compiling documents was held insufficient because it did not expressly identify the remedy, assessment date, or governing legal basis.

If the FLD/FAN contains several issues, protest each disputed issue separately. An issue left unchallenged—or challenged without supporting facts and law—may be treated as undisputed, making the related assessment final and collectible. Pay any amount expressly conceded after confirming the correct payment instructions and computation.

Where and how to file

File the protest with the Commissioner’s duly authorized representative who signed the PAN and FLD/FAN, as directed by RMC No. 11-2014. Depending on the case, this may involve the responsible Revenue Region, Large Taxpayers Service, or National Office unit.

Before filing:

Confirm the receiving office from the FLD/FAN and the signatory’s office;
Prepare a complete receiving copy;
Ask the BIR to stamp the receiving copy with the date, time, office, and name or identifying mark of the receiving personnel;
Obtain an official document reference or acknowledgment when available;
Preserve proof of delivery for any registered-mail or courier submission; and
Do not assume that ordinary email, eAFS, ORUS, or another portal is an authorized protest channel unless the notice or a specific BIR issuance expressly permits it.

File early. A protest delivered to the wrong office or dispatched without reliable proof may create a dispute about whether it was timely and properly filed.

Review the assessment for both factual and legal errors

Reconcile the numbers

Compare the assessment with:

Filed returns and electronic acknowledgments;
Tax-payment confirmations;
General and subsidiary ledgers;
Audited financial statements and tax reconciliations;
Withholding tax certificates and alphalists;
VAT schedules, invoices, and customs documents;
Contracts, billing records, and bank records;
Tax credit certificates, prior-year carryovers, and approved incentives; and
Third-party information cited by the BIR.

Prepare a schedule showing each BIR adjustment, the taxpayer’s position, supporting document, legal basis, and corrected amount.

Check the BIR’s authority and audit scope

Review the Letter of Authority or electronic Letter of Authority for the correct taxpayer, TIN, taxable year, tax types, assigned revenue officers, and scope. Under RMO No. 1-2026, the BIR now generally uses a single-instance audit framework for a taxable year and requires specified information in an eLA, subject to stated exceptions.

Overlapping authorities, unauthorized officers, examinations beyond the covered period or tax types, and improper reassignment can be material. Their legal effect is fact-sensitive; not every internal procedural irregularity automatically voids an assessment.

Check prescription

As a general rule, the BIR must assess within three years after the last day prescribed for filing the return, or from actual filing if the return was filed late. Different rules can apply to a false or fraudulent return with intent to evade tax, failure to file a return, valid written waivers, amended returns, and statutory suspensions. Under Section 222, the assessment period may extend to 10 years from discovery in specified fraud or non-filing cases.

Prescription calculations are technical. Review the return date, legal due date, assessment issuance and service dates, waivers, and every event claimed to suspend the period.

Check due process

The FLD/FAN must inform the taxpayer in writing of the material facts and legal basis for the assessment. The FDDA must likewise state its factual and legal basis and identify itself as the final decision. A mere restatement of figures or conclusions may be insufficient, but the adequacy of the notice must be judged from the complete documents.

Also check whether:

A required PAN was issued and properly served;
The taxpayer received the full response period;
The assessment fixed a definite liability and made a valid demand;
The proper official issued and signed the notices; and
Service complied with the permitted modes.

What happens if the BIR does not act within 180 days?

Inaction does not automatically cancel the assessment.

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

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

The Supreme Court recognized these options in Lascona Land Co., Inc. v. Commissioner of Internal Revenue. Once the taxpayer chooses to appeal the inaction, the taxpayer cannot also wait for and pursue a later administrative decision.

The correct starting date for the 180 days depends on whether the protest is a reconsideration or reinvestigation and whether the matter is already an administrative appeal to the Commissioner. A single miscount can defeat CTA jurisdiction, so have the complete timeline checked before choosing.

Appealing to the Court of Tax Appeals

A CTA appeal is initiated through a petition for review before a CTA Division. It is formal court litigation, not another BIR letter. The petition must establish the CTA’s jurisdiction and timeliness, state the material facts and legal issues, and comply with verification, certification, annex, service, fee, and other requirements under the Revised Rules of the Court of Tax Appeals.

Current CTA rules also require electronic transmittal of court submissions. Under CTA En Banc Resolution No. 8-2024, noncompliance with the applicable electronic-copy and 24-hour requirements can cause a paper pleading to be treated as not filed. Confirm the latest filing instructions with the CTA and counsel before the deadline.

A CTA appeal does not automatically suspend collection. Under Republic Act No. 9282, the CTA may suspend collection when it finds that collection could 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.

Interest, surcharges, and payment while protesting

Prepayment is generally not required merely to file the administrative protest or an assessment appeal to the CTA. However, a protest does not necessarily stop statutory interest from accumulating, and a CTA petition alone does not prevent collection.

Under RR No. 21-2018, the general interest rate is currently 12% per year while the BSP legal interest rate remains 6%. Deficiency and delinquency interest may not be imposed simultaneously for periods governed by the TRAIN amendments.

Micro and small taxpayers receive special concessions under the Ease of Paying Taxes Act and RR No. 6-2024, including a 50% reduction of the Section 249 interest rate—currently resulting in 6%—and a reduced 10% civil-penalty rate for penalties covered by Section 248. Fraud-related penalties remain subject to separate rules.

Before making a partial or full payment, assess its effect on the dispute, interest, collection exposure, and any possible refund deadline.

Evidence to preserve

Keep both physical and electronic copies of:

Every BIR notice, including all pages and annexes;
Envelopes, registry notices, courier labels, return cards, and delivery tracking;
The eLA or LOA and any amendments, replacements, or reassignment documents;
PAN responses, protests, administrative appeals, and supporting-document submissions;
BIR-stamped receiving copies and electronic acknowledgments;
Minutes and notes of discrepancy discussions and conferences;
Returns, amendments, filing acknowledgments, and payment confirmations;
Books, ledgers, invoices, receipts, contracts, bank records, and reconciliations;
Withholding certificates, tax credits, incentive registrations, and exemption documents;
Emails and letters exchanged with revenue officers;
Proof of the representative’s authority; and
A dated chronology of every audit, assessment, protest, decision, and collection event.

Preserve native electronic files and metadata where possible. Do not annotate or alter the only copy of a notice.

Common mistakes

Treating a PAN response as the formal protest against the FLD/FAN;
Filing a generic “we disagree” or “documents to follow” letter;
Failing to state whether the protest is reconsideration or reinvestigation;
Omitting the assessment date, factual grounds, or legal basis;
Contesting only the total while leaving individual adjustments unanswered;
Missing the reinvestigation document deadline;
Filing with the revenue officer instead of the authorized signatory’s office;
Having no stamped receiving copy or reliable proof of delivery;
Assuming 180 days of inaction cancels the assessment;
Filing another BIR motion and assuming it extends the CTA deadline;
Assuming a CTA appeal automatically stops garnishment, distraint, or levy; or
Relying on an apparent procedural defect without preserving substantive defenses and evidence.

When professional help is urgent

Contact a Philippine tax lawyer promptly if:

The 30-day protest or appeal deadline is approaching;
You received an FDDA, final demand, collection letter, warrant, levy, or garnishment;
The BIR alleges fraud, intentional evasion, fake transactions, or substantial underdeclaration;
A criminal complaint, subpoena, or referral is mentioned;
The assessment threatens payroll, bank accounts, operations, or essential property;
Receipt or service of a notice is disputed;
The assessment covers old periods, waivers, or prescription issues;
Multiple or overlapping eLAs cover the same year;
Important records are missing or held by third parties; or
The amount is material enough that interest, a bond, or an incorrect procedural choice could cause serious harm.

Frequently asked questions

Can I protest a PAN?

You should respond to a PAN within 15 days, but the formal Section 228 administrative protest is filed against the FLD/FAN. If an FLD/FAN follows, file a separate protest within 30 days even if you already submitted a detailed PAN response.

What if I missed the PAN response deadline?

The BIR may issue an FLD/FAN based on its findings. You ordinarily still have 30 days from receipt of the FLD/FAN to file the formal protest. Responding late to the PAN does not extend that period.

Must I pay the assessment before filing a protest?

Generally, no. But interest may continue, and collection risks can arise once an assessment becomes final or during a CTA case. Consider payment and suspension-of-collection options with counsel.

Can I submit documents after 60 days?

For a reinvestigation, all relevant supporting documents must be submitted within 60 days from filing the protest. Late new or additional evidence may be rejected. A reconsideration does not carry the same 60-day period because it relies on existing records.

Does BIR inaction after 180 days mean I won?

No. You may appeal the inaction within the following 30 days or wait for a final BIR decision. Neither option automatically cancels the assessment.

Can an accountant or employee sign the protest?

The taxpayer or a properly authorized representative or tax agent may file it. The required authority depends on whether the taxpayer is an individual, corporation, partnership, estate, or other entity. Attach clear proof of authority.

What if the notice was sent to an old address?

Service validity depends on the registered address, any properly reported address change, the actual mode of service, and who received the notice. Because service at a registered or known address—and service on an appointed tax agent—may be effective, obtain immediate advice and preserve the envelope and delivery records.

Is a late BIR response to my PAN automatically fatal to the assessment?

Not necessarily. RMC No. 11-2014 states that an FLD/FAN issued more than 15 days after the PAN response may remain valid if issued within the statutory assessment period, although the internal delay may constitute an administrative infraction.

Official legal references

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, protest type, signatory, taxable periods, and complete audit record. Primary sources were checked through August 3, 2026.