Quick answer

To dispute a BIR deficiency tax assessment, file a valid written protest against the Formal Letter of Demand and Final Assessment Notice (FLD/FAN) within 30 calendar days from receipt. Choose either a request for reconsideration, based only on the existing record, or a request for reinvestigation, based on newly discovered or additional evidence. If you choose reinvestigation, submit all relevant supporting documents within 60 days from filing the protest.

Missing these deadlines can make the assessment final, executory, and demandable. A letter merely asking for more time, a conference, or a payment arrangement may not qualify as a protest. Even if the assessment appears void, do not ignore it—raise every objection in a timely protest and preserve proof of filing.

These rules concern national internal revenue tax assessments issued by the BIR. Local business taxes, real-property taxes, customs duties, and tax shown as payable on your own return follow different procedures.

Identify the document you received

The correct response depends on the notice:

Document	What it means	Usual immediate action
Notice of Discrepancy or audit correspondence	The audit is still being discussed	Answer within the period stated and submit supporting records
Preliminary Assessment Notice (PAN)	A proposed deficiency assessment	Reply within 15 days from receipt
FLD/FAN	The formal assessment and demand for payment	File a valid administrative protest within 30 days from receipt
Final Decision on Disputed Assessment (FDDA)	The BIR’s decision on the protest	Appeal administratively or to the CTA, as applicable, within 30 days from receipt
Collection letter, Final Notice Before Seizure, warrant of distraint or levy, or warrant of garnishment	Collection action may have begun	Obtain legal help immediately; the document may affect an appeal or injunction deadline

A reply to a PAN is not the same as the formal protest against an FLD/FAN. The PAN reply is technically optional, but it is often the best opportunity to correct facts and computations before a final assessment is issued. Failure to reply allows the BIR to treat the taxpayer as in default and proceed to the FLD/FAN.

The essential deadlines

15 days from receipt of the PAN: Submit the PAN reply and supporting records.
30 days from receipt of the FLD/FAN: File the written protest.
60 days from filing a request for reinvestigation: Submit all relevant supporting documents.
180 days for BIR action:
- For reconsideration, generally counted from filing of the protest.
- For reinvestigation, generally counted from submission of the required supporting documents within the 60-day period.
30 days after the 180-day period expires: If choosing to appeal the BIR’s inaction to the Court of Tax Appeals.
30 days from receipt of an FDDA or other final adverse decision: File the appropriate administrative appeal or CTA petition.

Treat these as strict calendar-day deadlines. Preserve the actual date and manner of receipt. If the last day falls on a weekend, holiday, declared non-working day, or a period covered by a special BIR extension, verify the applicable rule and current BIR issuance instead of assuming an extension.

Step 1: Establish the date of receipt

The deadline normally runs from receipt, not from the date printed on the notice. Immediately preserve:

The complete notice and all annexes;
The envelope, registry notice, courier pouch, tracking record, and delivery receipt;
The name and position of the person who accepted personal service;
Photographs or CCTV records of service, if available;
The taxpayer’s BIR registration address at the time of service; and
Any authority appointing a tax agent or representative.

Service on an accredited tax agent appointed by the taxpayer may be treated as service on the taxpayer. Notices may also be validly served at the registered or known address through the modes allowed by the regulations. Moving offices or closing operations without updating the BIR registration can cause serious problems; non-receipt does not automatically defeat service at the address in the BIR database.

If the receipt date is disputed, state the taxpayer’s position in the protest and attach the available proof. As a precaution, file using the earliest defensible receipt date.

Step 2: Review the assessment before drafting

Compare the PAN, FLD/FAN, audit working papers, returns, and accounting records issue by issue. Check:

Whether the audit was supported by a valid Letter of Authority and conducted by authorized revenue officers;
Whether the correct taxpayer, taxable period, and tax type were covered;
Whether a required PAN was issued and properly served;
Whether the BIR allowed the taxpayer the full PAN-response period;
Whether the FLD/FAN states the specific facts and legal bases for each adjustment;
Whether the computations reconcile with the returns, books, payments, and withholding certificates;
Whether documents already submitted were considered;
Whether the assessment was issued within the applicable prescriptive period; and
Whether any waiver extending the assessment period was validly executed before the existing period expired.

The ordinary period to assess is generally three years from the statutory filing deadline or the actual filing date when the return was filed late. Different rules may apply to a false return, a fraudulent return with intent to evade tax, failure to file a return, or a valid written extension. Prescription is highly document-dependent, so the return-filing records and any waivers must be reviewed carefully.

A valid Letter of Authority and written disclosure of the assessment’s factual and legal bases are substantive due-process requirements. The Supreme Court has repeatedly treated assessments issued without the required authority or process as vulnerable to invalidation. Nevertheless, alleged invalidity does not justify missing the protest deadline.

When the BIR may issue an FLD/FAN without a PAN

A PAN is generally required, but Section 228 of the Tax Code allows an outright FLD/FAN when:

The deficiency results from a mathematical error apparent on the face of the return;
There is a discrepancy between tax withheld and the amount actually 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 the succeeding taxable year;
Excise tax on excisable articles was not paid; or
An article bought or imported by an exempt person was later sold, traded, or transferred to a non-exempt person.

If none of these exceptions applies, failure to issue the required PAN should be expressly raised.

Step 3: Choose the correct protest

Request for reconsideration

Choose reconsideration when the BIR can resolve the dispute using records already available to it. It may raise questions of fact, law, or both, but it does not contemplate new evidence.

The special 60-day supporting-document deadline does not apply to reconsideration. That does not mean the protest can be vague: identify the existing records that support every argument.

Request for reinvestigation

Choose reinvestigation when the taxpayer needs to present newly discovered or additional documents or evidence. The protest should identify the new or additional evidence intended to be submitted.

All relevant supporting documents must be submitted within 60 days from filing the protest. The BIR’s rules direct that evaluation be based on documents submitted within that period, and late evidence may be rejected.

The two remedies are mutually exclusive. A protest is generally treated as a request for reconsideration unless it clearly states that it is a request for reinvestigation. If the case depends on records not previously submitted, labeling it reconsideration can be a costly mistake.

Step 4: Draft a valid, issue-specific protest

The protest should contain at least:

The taxpayer’s registered name, TIN, address, and contact details;
The assessment notice number, date, tax type, taxable period, and amount;
The date and manner the FLD/FAN was received;
A clear statement that the taxpayer protests the assessment, in whole or in identified part;
An express choice between reconsideration and reinvestigation;
For reinvestigation, a description of the new or additional evidence to be submitted;
Separate factual and legal arguments for every disputed adjustment;
The applicable statutes, regulations, and controlling jurisprudence;
Corrected computations, when the amount is disputed;
A list of attached or previously submitted evidence;
The relief requested, such as cancellation or reduction of the assessment; and
The taxpayer’s or duly authorized representative’s signature and proof of authority.

Do not use a blanket statement such as “the assessment is erroneous and contrary to law.” Under the regulations, an issue not specifically disputed with supporting facts and legal grounds may be treated as undisputed. The corresponding tax can then become final and collectible even while other issues remain under protest.

If part of the assessment is accepted, clearly identify the accepted and disputed portions. Coordinate any partial payment with the appropriate BIR office and retain the filed return or payment form and official proof of payment.

Step 5: File with proof

File with the BIR office identified in the FLD/FAN or otherwise officially designated to receive the protest. Unless an applicable issuance or written instruction authorizes another method, the safest practice is personal filing by the taxpayer or an authorized representative.

Obtain:

A complete receiving copy bearing the BIR date-and-time stamp;
The receiving office and name or identifying mark of the receiving personnel;
Proof of the representative’s authority; and
An indexed copy of everything filed.

Do not rely solely on an informal email to a revenue officer. Temporary electronic-filing arrangements issued for exceptional periods do not necessarily create a permanent general filing channel. If using courier, email, or another method, confirm in writing that the correct office accepts that mode and preserve proof of timely receipt—not merely proof that the document was sent.

Current BIR operational circulars may create limited deadline adjustments during government work suspensions or special office schedules. These are situation-specific and should be checked against the taxpayer’s office, due date, and location.

Step 6: Submit evidence and track the 180-day period

For reinvestigation, submit a paginated and indexed evidence package within 60 days. Use a transmittal letter identifying the original protest, the assessment, and every enclosed document. Obtain a stamped receiving copy.

Useful evidence commonly includes:

Tax returns, filing confirmations, and proof of payment;
Books of accounts, trial balances, ledgers, and reconciliations;
Invoices and other supporting documents applicable to the period;
Withholding tax certificates and alphalists;
Contracts, purchase orders, delivery records, and bank statements;
Audited financial statements and schedules;
Correspondence and records previously given to the BIR;
The Letter of Authority and any replacement or reassignment authority;
PAN and FLD/FAN computations;
Proof of the dates returns and amended returns were filed; and
Any waivers of the statute of limitations.

Maintain a deadline sheet showing the protest date, document-submission date, 180th day, and the 30-day CTA window following inaction. Confirm the actual date from original records rather than relying on a verbal calculation by the examiner.

Step 7: Act immediately on the FDDA

An FDDA should identify the facts and legal grounds for the decision and state that it is final. Its substance matters more than its title, so any letter that clearly adopts a final position and demands payment should be reviewed urgently.

If the FDDA was 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 Court of Tax Appeals; or
Elevate the matter to the Commissioner through a request for reconsideration.

An administrative appeal to the Commissioner cannot be a reinvestigation. Only reconsideration is available, and only issues addressed in the authorized representative’s decision will be entertained.

If the adverse decision was issued by the Commissioner personally, the remedy is generally a petition for review with the CTA within 30 days. Filing another motion for reconsideration with the Commissioner does not suspend or restart the CTA deadline.

Step 8: Decide what to do if the BIR does not act

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

Appeal the inaction to the CTA within 30 days after the 180-day period; or
Wait for the BIR’s final decision and appeal within 30 days from receiving it.

The Supreme Court confirmed this choice in Lascona Land Co. v. CIR and later applied it to an administrative appeal in Light Rail Transit Authority v. BIR. Once the taxpayer appeals the inaction, the taxpayer cannot also wait for and pursue a later administrative decision as a separate remedy.

Waiting is legally possible, but it should be a deliberate, documented decision. Later BIR collection correspondence may arguably communicate a final denial, depending on its contents, and could trigger a new 30-day period.

Common mistakes that can make an assessment final

Protesting only the PAN and failing to protest the later FLD/FAN;
Counting from when management learned of the assessment instead of its legal receipt;
Filing after the 30-day period;
Asking for an extension instead of filing a complete, valid protest on time;
Failing to choose reconsideration or reinvestigation;
Calling the protest reconsideration while relying on new evidence;
Omitting facts and legal grounds for one or more adjustments;
Missing the 60-day evidence deadline for reinvestigation;
Sending documents without a stamped transmittal or proof of receipt;
Treating an FDDA as another audit letter;
Filing another BIR motion and assuming it stops the CTA deadline;
Failing to monitor service at the registered address or on the appointed tax agent; and
Assuming a CTA appeal automatically stops collection.

Under the BIR’s 2026 audit-consolidation rules, a properly issued Consolidated FAN that expressly supersedes prior notices may give a fresh 30-day protest period from receipt. Confirm that the consolidated notice satisfies the requirements of RMO No. 6-2026; do not assume every revised computation restarts the deadline.

Collection and requests to suspend it

A timely and valid administrative protest ordinarily prevents the disputed assessment from becoming a delinquent account merely because the taxpayer refused to pay. The Supreme Court’s 2025 decision in CIR v. Stradcom Corporation reiterates that collection must rest on a valid assessment and that premature warrants may be unlawful.

Once the case reaches the CTA, however, filing the appeal does not automatically suspend payment, distraint, levy, garnishment, or sale. The taxpayer may ask the CTA to suspend collection when collection may jeopardize the interests of the government or the taxpayer. The request requires evidence and may involve a deposit or surety bond, subject to the court’s determination.

Seek urgent tax counsel upon receiving:

An FDDA with fewer than 30 days remaining;
A Preliminary Collection Letter or Final Notice Before Seizure;
A warrant of distraint, levy, or garnishment;
Notice that a bank account has been frozen;
A levy or scheduled sale of property;
A criminal referral, subpoena, or fraud allegation;
An assessment apparently served at an old address; or
Conflicting BIR letters that make the final decision or deadline unclear.

Frequently asked questions

Must I pay before protesting the FLD/FAN?

Generally, no. A deficiency assessment may be administratively protested without first paying the disputed amount. Any accepted portion may be paid separately. This differs from certain refund and local-tax procedures.

Can I protest only part of the assessment?

Yes, but every disputed issue must be identified and supported. The undisputed portion may become final, demandable, and subject to collection.

Can I submit supporting documents after 60 days?

For reinvestigation, the BIR may reject documents submitted after the 60-day period. Submit the complete evidence package on time and preserve proof of receipt.

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

The FLD/FAN must state the facts and legal bases for the assessment. Raise the defect in a timely protest together with all other factual and legal defenses. Do not simply disregard the notice.

Does replying to the PAN preserve my rights?

Not by itself. A PAN reply does not replace the separate protest that must be filed within 30 days from receipt of the FLD/FAN.

Can the BIR issue an FDDA before considering my timely PAN reply?

The BIR must observe the assessment sequence and the taxpayer’s opportunity to respond. The Supreme Court has invalidated assessments where the BIR prematurely issued the FLD/FAN before the PAN-response period expired. Raise the exact dates and attach proof.

Can I wait indefinitely after the 180-day period?

You may choose to await a final decision, but once a final adverse decision is received, the 30-day CTA period applies. Continuing correspondence and collection notices should be reviewed immediately because their substance may show that the BIR has finally denied the protest.

Do I need a lawyer or CPA?

A taxpayer may prepare an administrative protest, but legal and accounting assistance is strongly advisable when the assessment is substantial, several tax types are involved, prescription or audit authority is disputed, fraud is alleged, or an FDDA or collection warrant has been issued. CTA litigation is technical and should be handled well before the 30-day deadline.

Official sources

This article provides general legal information, not legal or tax advice for a particular assessment. Deadlines and remedies depend on the actual notices, service records, issuing official, taxable period, and documents. Sources and procedures were checked as of August 3, 2026.