Quick answer

To dispute a BIR deficiency tax assessment, file a written administrative protest against the Formal Letter of Demand and Final Assessment Notice (FLD/FAN) within 30 calendar days from receipt. State whether you seek:

Reconsideration — re-evaluation using records already available to the BIR; or
Reinvestigation — re-evaluation using newly discovered or additional evidence.

Address every disputed assessment and issue separately, explaining the supporting facts and legal basis. For a reinvestigation, submit all relevant supporting documents within 60 days from filing the protest. Missing these deadlines can make the assessment final, executory, and demandable. These requirements come from Section 228 of the National Internal Revenue Code and Revenue Regulations No. 18-2013.

Do not wait for an informal meeting, settlement discussion, document request, or verbal assurance from a revenue officer. None ordinarily extends the protest deadline.

Identify what document you received

Not every BIR communication is protested in the same way.

Document	What it means	Immediate response
Notice of Discrepancy (NOD)	Initial audit discrepancies; not yet an assessment	Answer within the period stated in the notice and provide reconciliations or records
Preliminary Assessment Notice (PAN)	Proposed deficiency assessment	Submit a written reply within 15 days from receipt
FLD/FAN	Formal, protestable assessment and demand for payment	File a valid protest within 30 days from receipt
Final Decision on Disputed Assessment (FDDA)	Decision on the protest	Appeal or seek the permitted administrative review within 30 days
Collection letter, warrant of distraint or levy, or garnishment notice	Collection action, usually based on an assessment the BIR considers final	Obtain legal help immediately and verify whether a timely protest or appeal remains pending

A PAN reply is important, but it is not a substitute for protesting the later FLD/FAN. Conversely, a letter responding only to an NOD or PAN generally will not preserve the right to contest a subsequently issued FLD/FAN.

Check the date and validity of service immediately

Write down the exact date the notice was received and who received it. Preserve:

The original envelope, registry notice, courier pouch, waybill, and tracking record;
The receiving stamp or acknowledgment;
Email headers, if the BIR also sent an electronic copy;
Building security logs or mailroom records;
The name and position of the person who accepted delivery; and
Any authorization appointing a tax agent or representative.

Assessment notices may be served personally, through substituted service, or by mail or courier under RR No. 18-2013. Service on a duly appointed tax agent may be treated as service on the taxpayer. RMO No. 40-2019 also provides rules on when service is considered complete.

Treat the statutory periods as calendar-day deadlines and file early. The day of receipt is ordinarily excluded when counting, but do not rely on an assumed weekend, holiday, office-closure, or mailing extension without checking the rule and any current BIR advisory applicable to the specific filing.

As of August 3, 2026, RMC No. 35-2026 contains a narrow temporary rule: while the specified National Office work arrangement remains effective, a Friday deadline for filing a request for reconsideration of an FDDA at the National Office moves to the next business day when personnel are working on-site. It does not generally extend initial FLD/FAN protests, supporting-document deadlines, or CTA appeals.

Respond to the PAN, if one was issued

The BIR generally must issue a PAN that states in detail the facts and legal basis for the proposed assessment. A written reply is due within 15 days from receipt. Use the reply to correct factual errors, submit reconciliations, identify unsupported assumptions, and raise procedural or legal objections.

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

A mathematical error appearing on the face of the return;
A discrepancy between tax withheld and tax actually remitted by the withholding agent;
Carryover of the same excess creditable withholding tax for which a refund or tax credit was claimed;
Unpaid excise tax on excisable articles; or
Transfer to a non-exempt person of an article acquired locally or imported by an exempt person.

Outside these exceptions, failure to issue and properly serve a required PAN may be a due-process defense. Raise it in the FLD/FAN protest even if you believe the assessment is void; do not simply ignore the FLD/FAN.

Choose the correct kind of protest

Request for reconsideration

Choose reconsideration when the protest can be decided from records already available to the BIR. Typical issues may include:

An incorrect interpretation of a tax provision;
Duplicate or mathematical adjustments;
Failure to credit payments or withholding taxes already shown in the records;
An assessment outside the applicable limitation period; or
A due-process or authority issue established by existing documents.

The special 60-day supporting-document period under RR No. 18-2013 does not apply to reconsideration. Nevertheless, attach or clearly identify the existing records on which the protest depends.

Request for reinvestigation

Choose reinvestigation when you need the BIR to consider newly discovered or additional evidence, such as missing invoices, contracts, reconciliations, third-party certifications, or accounting schedules.

The protest must identify the additional evidence you intend to present. Submit all relevant supporting documents within 60 days from filing the protest. Late documents may be rejected, and failure to comply can cause the assessment to become final.

The choice matters. RMO No. 26-2016 states that a protest is treated as a request for reconsideration unless it clearly identifies itself as a request for reinvestigation. Filing one remedy precludes filing the other against the same FLD/FAN.

What the protest letter should contain

There is no universal BIR form that replaces a properly prepared protest letter. At minimum, include:

The taxpayer’s registered name, TIN, address, and contact details;
The assessment numbers, dates, tax types, taxable periods, and amounts involved;
The date the FLD/FAN was actually received;
A clear heading stating either Request for Reconsideration or Request for Reinvestigation;
A statement identifying every assessment and issue being disputed;
For each issue:
- The BIR’s finding;
- The material facts;
- The specific reason the finding is incorrect;
- The applicable statute, regulation, controlling decision, or other legal authority; and
- The supporting document or schedule;
For reinvestigation, a description of the newly discovered or additional evidence to be submitted;
The exact relief requested, such as cancellation or reduction of a specified assessment;
A reservation of rights regarding interest and penalties that depend on the disputed basic tax; and
The signature of the taxpayer or properly authorized representative, with proof of authority where applicable.

A statement such as “we disagree with the assessment” is not enough. Under RR No. 18-2013, issues not supported by facts and legal grounds may be treated as undisputed. Any portion not protested can become final and collectible even while other portions remain under review.

File with proof of timely receipt

Follow the filing instructions and office identified in the FLD/FAN. If the notice is unclear, confirm the proper receiving office before the deadline.

The safest record is a complete copy bearing the BIR’s receiving stamp, date, time, and the name or identifying mark of the receiving office. If another permitted delivery method is used, preserve reliable proof that the correct BIR office actually received the complete protest on time. Do not assume that an ordinary email, a message to the examining revenue officer, or mailing on the final day constitutes a valid filing.

Keep an identical electronic and paper copy of everything submitted. Prepare an exhibit index and obtain proof of receipt for every later submission. A cover letter should list each enclosed document so the BIR cannot reasonably dispute what was delivered.

Build an issue-by-issue evidence file

The required evidence depends on the tax type and assessment. Common records include:

Filed returns, amended returns, payment confirmations, and BIR forms;
Audited financial statements, trial balances, general ledgers, and subsidiary ledgers;
Invoices or official receipts applicable to the audited period;
Withholding tax certificates, alphalists, and proof of remittance;
Contracts, purchase orders, delivery records, and acceptance documents;
Bank statements and payment records;
Inventory, importation, payroll, and fixed-asset schedules;
Reconciliations between tax returns, financial statements, books, and third-party information;
Proof of exemptions, incentives, treaty entitlement, or registration;
The Letter of Authority and documents identifying the authorized revenue officers;
Waivers of the statute of limitations and proof of when each was executed; and
All NOD, PAN, FLD/FAN, FDDA, protest, and collection correspondence.

Do not alter original records or create documents that did not exist. If a reconciliation or explanatory schedule is prepared later, label it accurately and show how it ties to contemporaneous source records.

Check both procedural and substantive defenses

A proper protest should address the amount of tax and any procedural defect supported by the documents. Matters that may require examination include:

Whether the assessment was issued and served within the applicable prescriptive period;
Whether the audit was conducted by officers covered by a valid Letter of Authority;
Whether a required PAN was issued and properly served;
Whether the PAN and FLD/FAN state the material facts and legal basis for each assessment;
Whether the BIR considered the taxpayer’s explanation and records;
Whether the FLD/FAN reflects a genuine assessment rather than a predetermined conclusion;
Whether service was made at the registered or known address or on an authorized person;
Whether payments, credits, or withholding taxes were omitted;
Whether the BIR used incorrect tax rates, periods, classifications, or assumptions; and
Whether interest and penalties were computed on the correct base and for the correct periods.

Section 228 requires the taxpayer to be informed in writing of the law and facts on which the assessment is based; otherwise, the assessment is void. An FDDA must likewise state its factual and legal bases and identify itself as the final decision. Even when a notice appears defective, preserve the objection through a timely protest or appeal rather than assuming that the defect automatically stops collection.

Track the 180-day decision period

The starting date depends on the remedy:

For reconsideration, RR No. 18-2013 counts 180 days from filing the protest.
For reinvestigation, it counts 180 days from submission of the supporting documents within the 60-day period.

Record the applicable start date and calculate the 180th day in writing.

If the BIR does not act within 180 days, the taxpayer has two mutually exclusive choices:

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

The Supreme Court confirmed these alternatives in Lascona Land Co. v. CIR, Light Rail Transit Authority v. BIR, and Mannasoft Technology Corp. v. CIR. Once the taxpayer chooses to appeal the inaction, the taxpayer cannot also wait for and later appeal a decision on the same protest.

Because the correct starting date can depend on the protest’s wording and the documentary record, obtain advice before using the inaction route.

What to do after receiving an FDDA

First determine who issued the FDDA.

FDDA issued by the Commissioner of Internal Revenue

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 stop or restart the CTA appeal period.

FDDA issued by the Commissioner’s authorized representative

Within 30 days from receipt, choose either:

Appeal directly to the CTA; or
Elevate the matter to the Commissioner through a request for reconsideration.

The administrative appeal to the Commissioner is limited to issues addressed in the authorized representative’s decision. A new request for reinvestigation and new evidence are not allowed at this stage.

If the Commissioner fails to act on that administrative appeal within 180 days from filing, the taxpayer may appeal to the CTA within 30 days after the 180 days expire or wait for the Commissioner’s decision and appeal within 30 days from receipt.

Do not file both routes or assume that one automatically preserves the other.

Appealing to the Court of Tax Appeals

CTA proceedings are judicial cases governed by jurisdictional and procedural rules. The appeal is generally initiated by a petition for review in the appropriate CTA Division within the 30-day statutory period. The CTA’s authority over BIR disputed assessments and inaction is set out in Republic Act No. 1125, as amended by RA No. 9282, and the procedure appears in the Revised Rules of the Court of Tax Appeals.

Do not assume that a request for an extension will be granted. Engage tax counsel early enough to prepare the petition, verification, certification, supporting documents, filing fees, and any application concerning collection.

An appeal does not automatically suspend tax collection. The CTA may suspend collection when the statutory requirements are met and may require a cash deposit or surety bond of up to twice the amount claimed. Any request for suspension must be supported by evidence and raised properly before the CTA. The Supreme Court discussed this remedy in CIR v. CTA and American Wire & Cable Co..

Common mistakes that can end the case

Treating a PAN reply as the protest against the FLD/FAN;
Filing after the 30-day period because discussions with the examiner continued;
Failing to identify whether the protest is reconsideration or reinvestigation;
Choosing reconsideration while intending to submit new evidence later;
Missing the 60-day document deadline for reinvestigation;
Disputing only the total amount without addressing each adjustment;
Omitting facts and legal grounds for one or more issues;
Sending the protest to the wrong office or having no proof of receipt;
Counting the 180 days from the wrong event;
Filing another motion with the Commissioner and assuming it stops the CTA period;
Appealing the FLD/FAN directly to the CTA without first making a valid administrative protest;
Assuming a CTA appeal automatically stops distraint, levy, garnishment, or sale; and
Treating a compromise or abatement application as a substitute for preserving protest and appeal deadlines.

When professional help is urgent

Consult a Philippine tax lawyer or experienced tax practitioner immediately if:

Fewer than seven days remain before a protest or appeal deadline;
You received an FDDA, collection letter, warrant, garnishment notice, levy, or seizure notice;
The assessment alleges fraud, falsity, deliberate non-filing, or possible criminal violations;
The BIR served the notice on someone whose authority is disputed;
You did not receive the PAN or FLD/FAN and learned of the assessment only through collection;
Multiple assessments, consolidated FANs, different tax periods, or different BIR offices are involved;
The assessment concerns withholding taxes, cross-border transactions, tax incentives, treaty relief, or a large amount;
There are disputed waivers or prescription issues; or
The BIR is collecting while a timely protest, administrative appeal, or CTA appeal is still pending.

Frequently asked questions

Must I pay the assessment before filing an administrative protest?

Generally, no. Section 228 allows a timely administrative protest without prior payment. However, interest may continue to accrue as provided by law, and a later CTA appeal does not automatically suspend collection.

Can I protest only part of the FLD/FAN?

Yes, but the unprotested portion may become final, executory, and demandable. Clearly identify both the disputed and accepted portions. Obtain advice before making partial payment because payment can affect later claims and litigation positions.

Can I submit supporting documents after 60 days?

For reinvestigation, all relevant supporting documents should be submitted within 60 days from filing the protest. Do not expect late evidence to be accepted. Reconsideration is based on existing records and is not a way to reserve an unlimited period for new evidence.

What if the FLD/FAN does not explain the assessment?

Section 228 requires the factual and legal basis to be stated in writing. Raise the defect expressly in a timely protest, identify what is missing, and preserve the original notice and attachments.

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 and appeal within 30 days from receipt. The choices are mutually exclusive.

Can I email the protest?

Do not rely on ordinary email unless the assessment, a controlling BIR issuance, or the proper receiving office expressly authorizes that filing method. Use a method that produces reliable proof of timely receipt by the correct office.

Does applying for compromise or abatement extend the protest deadline?

Do not assume so. A compromise or abatement application is a separate remedy with different requirements. Preserve the 30-day protest and appeal deadlines unless a controlling written rule or court order clearly provides otherwise.

What if a collection warrant arrives while my protest is pending?

Act immediately. Preserve proof of the timely protest and supporting-document submission, notify counsel, and assess the appropriate administrative or CTA remedy. A valid pending protest ordinarily means the deficiency assessment has not yet become final, but the correct response depends on the documents and procedural history.

Official sources

This article provides general legal information, not legal or tax advice for a particular assessment. Deadlines and available remedies depend on the actual notices, proof of service, protest wording, issuing official, and case history. Sources and current procedures were checked as of August 3, 2026.