Quick answer

To challenge a BIR deficiency-tax assessment, file a valid written request for reconsideration or reinvestigation within 30 days from receipt of the Formal Letter of Demand and Final Assessment Notice (FLD/FAN). Address every disputed tax and issue, identify the assessment and receipt dates, and state the supporting facts and legal grounds.

If you choose reinvestigation, submit all relevant supporting documents within 60 days from filing the protest. Missing the 30-day protest period—or leaving an issue unsupported—can make the assessment, or that particular issue, final, executory, and demandable.

A Preliminary Assessment Notice (PAN) is different. It ordinarily gives the taxpayer 15 days from receipt to respond, but that response does not replace the later protest against the FLD/FAN.

Because these periods are short and generally jurisdictional, record the exact date and manner of service immediately. Do not calculate the deadline merely from the date printed on the notice.

First identify what the BIR sent

The correct remedy depends on the document received.

Notice for Informal Conference

Under Revenue Regulations No. 7-2018, the BIR may first issue a written notice identifying audit discrepancies and inviting the taxpayer to an informal conference. The conference ordinarily cannot extend beyond 30 days from receipt of the notice.

Use this stage to reconcile records, obtain the revenue officer’s computations, and submit explanations. It is not yet the formal Section 228 protest stage.

Preliminary Assessment Notice

A PAN states the proposed deficiency taxes and should explain the supporting facts and legal bases. Under Revenue Regulations No. 18-2013, the taxpayer generally has 15 days from receipt to respond.

A detailed PAN reply may prevent incorrect findings from reaching the final-assessment stage. Nevertheless, replying to the PAN does not eliminate the need to protest a later FLD/FAN.

A PAN is not required in the limited cases stated in Section 228 of the National Internal Revenue Code, including certain facial mathematical errors, discrepancies between taxes withheld and remitted, improper carryover of an amount simultaneously claimed for refund or tax credit, unpaid excise tax, and specified transfers of tax-exempt articles to non-exempt persons. In those cases, the BIR may issue an FLD/FAN directly.

Formal Letter of Demand and Final Assessment Notice

The FLD/FAN is the assessment that must ordinarily be protested within 30 days from receipt. It normally contains the amount demanded, assessment numbers, taxable periods, penalties, and the factual and legal bases for each deficiency.

Do not assume that a conference, telephone call, request for payment terms, PAN reply, or informal letter automatically constitutes a valid protest.

Final Decision on Disputed Assessment

An FDDA is the BIR’s decision on the protest. It should state the facts and legal authorities supporting the decision and indicate that it is final.

The next remedy and deadline depend on whether the decision was issued by the Commissioner of Internal Revenue or by a duly authorized representative.

The critical deadlines

Stage	General deadline	Starting point
Response to PAN	15 days	Receipt of PAN
Administrative protest against FLD/FAN	30 days	Receipt of FLD/FAN
Supporting documents for reinvestigation	60 days	Filing of protest
BIR action period on reconsideration	180 days	Filing of protest
BIR action period on reinvestigation	180 days	Submission of the required documents
Appeal from denial by an authorized representative	30 days	Receipt of decision
Appeal from the Commissioner’s final denial	30 days	Receipt of decision
CTA appeal based on BIR inaction	30 days	Expiration of the applicable 180-day period

Count each deadline carefully using the actual proof of receipt and the applicable procedural rules. If the last day falls on a day when the proper office is officially closed, obtain current advice on the applicable extension rule rather than assuming that late filing will be excused.

Choose between reconsideration and reinvestigation

The protest must identify its nature expressly.

Request for reconsideration

A request for reconsideration asks the BIR to reevaluate the assessment using the existing audit record. It ordinarily raises errors in the BIR’s appreciation of facts already on record, computations, or application of law.

The special 60-day document-submission period under RR No. 18-2013 does not apply in the same manner to reconsideration. Still, attach the documents already in the record that are necessary to make the arguments understandable, and identify where and when they were previously submitted.

Reconsideration may be appropriate when:

the dispute is primarily legal;
the BIR used an incorrect tax rate or formula;
the assessment ignored records already submitted;
the computation contains duplication or arithmetic errors; or
no genuinely new evidence is needed.

Request for reinvestigation

A request for reinvestigation asks the BIR to examine newly discovered or additional evidence. The protest should identify the additional evidence intended to be presented.

All relevant supporting documents must be submitted within 60 days from filing the protest. Failure to comply can prevent the taxpayer from disputing the assessment through new or additional evidence and may result in denial and finality under the applicable rules.

Reinvestigation may be appropriate when:

source documents were not previously considered;
third-party confirmations are needed;
the audit relied on incomplete schedules;
accounting records require reconstruction or reconciliation; or
the taxpayer has additional evidence directly refuting the assessment.

The choice affects both the evidence that may be considered and the starting point of the 180-day BIR action period. It should not be made casually.

What a valid protest should contain

Under RR No. 18-2013, the written protest should at least state:

whether it is a request for reconsideration or reinvestigation;
the date and identifying details of the assessment;
the date the FLD/FAN was received;
each tax type, taxable period, assessment number, and amount disputed;
the facts supporting the taxpayer’s position;
the applicable statutes, regulations, and jurisprudence;
the specific relief requested; and
for reinvestigation, the newly discovered or additional evidence to be submitted.

A practical protest usually also includes:

A clear opening statement. State that the taxpayer protests the identified FLD/FAN under Section 228 of the Tax Code.
A deadline statement. Show the date of receipt and why the protest is timely.
Separate assignments of error. Discuss every assessment item individually—for example, income tax, VAT, expanded withholding tax, compromise penalties, and interest.
A factual chronology. Explain the transaction, accounting treatment, return position, audit finding, and taxpayer’s response.
Issue-specific evidence. Cross-reference invoices, contracts, returns, ledgers, withholding certificates, bank records, reconciliations, and prior submissions.
Corrected computations. If the taxpayer admits part of an adjustment but disputes the rest, show the alternative computation precisely.
Requested disposition. Ask that the disputed assessment be cancelled, reduced, or recomputed, as supported by the facts.

A bare statement that the assessment is “incorrect,” “excessive,” or “contrary to law” is dangerous. Issues for which the protest does not state supporting facts and legal grounds may be treated as undisputed.

Protest every issue that is genuinely disputed

An FLD/FAN may cover several taxes and multiple adjustments within each tax.

If the taxpayer disputes only some issues, the assessment attributable to the undisputed issues may become final, executory, and demandable. The same risk exists when an issue is mentioned but no facts or legal basis are stated for it.

Prepare an issue matrix showing:

Assessment item	BIR basis	Amount	Taxpayer’s factual response	Legal basis	Supporting documents

This reduces the risk of accidentally abandoning an assessment item.

If part of the liability is admitted, distinguish it expressly from the protested portion and obtain advice about payment and its effect on the remaining dispute.

How to file and prove timely filing

Follow the filing instructions in the FLD/FAN and the rules of the BIR office that issued it. File with the correct office or official; delivering a protest to an unrelated BIR unit may not preserve the deadline.

Keep:

the complete signed protest and every annex;
the BIR-received copy showing the date, office, and receiving personnel;
registry receipts, tracking records, and proof of delivery if an authorized mailing method is used;
the envelope, registry notice, acknowledgment receipt, and other proof showing when the FLD/FAN arrived;
the authority of the signatory or representative;
an index of annexes and document-submission receipts; and
a deadline calendar for the 30-, 60-, and 180-day periods.

For a corporation, partnership, estate, or taxpayer acting through a representative, confirm that the signatory has appropriate authority. Include the relevant board authorization, secretary’s certificate, special power of attorney, or BIR accreditation and authorization documents when required.

Obtain written proof of actual receipt. A taxpayer should not rely solely on an employee’s recollection that documents were “left at the BIR.”

Check whether due process was followed

Section 228 requires the taxpayer to be informed in writing of the facts and law on which the assessment is based. An assessment that fails this requirement may be void.

Review the complete assessment record for questions such as:

Was a PAN issued and properly served when one was required?
Did the taxpayer receive a genuine opportunity to respond before the FLD/FAN was issued?
Did the PAN and FLD/FAN explain the factual and legal bases instead of merely listing amounts?
Were the notices served on the taxpayer or a properly authorized representative?
Was the assessment issued by the Commissioner or a duly authorized official?
Does the assessment state a definite amount and a clear demand for payment?
Was it issued within the applicable assessment period?
Did the BIR materially change the basis of the assessment without giving a meaningful opportunity to respond?

The Supreme Court has treated proper notice and receipt of the PAN as important components of tax-assessment due process. See Mannasoft Technology Corporation v. Commissioner of Internal Revenue.

These objections should be raised promptly in the protest. Do not ignore the 30-day deadline merely because the taxpayer believes the assessment is void. Filing a timely protective protest is ordinarily the safer course.

What happens after the protest

The BIR may request conferences, explanations, or additional information. Respond in writing and keep proof of every submission.

Participation in discussions does not suspend a statutory deadline unless a valid law, regulation, or written order clearly provides otherwise. Statements by an examiner that the case is “under review” should not be treated as an extension.

The BIR may:

cancel the assessment;
reduce or recompute it;
deny particular issues;
deny the protest in full; or
fail to act within the applicable 180-day period.

Review every later letter carefully. A communication that unequivocally resolves the protest and demands payment may trigger an appeal deadline even if its title is unusual. The substance and authority of the issuer matter, not merely the label placed on the document.

If an authorized representative denies the protest

When a duly authorized representative of the Commissioner denies the protest in whole or in part, the taxpayer generally has 30 days from receipt to choose between:

filing a petition for review with the Court of Tax Appeals; or
filing an administrative request for reconsideration with the Commissioner.

At the administrative-appeal level, no request for reinvestigation is allowed. Only issues raised in the authorized representative’s decision may be entertained by the Commissioner under RR No. 18-2013.

Do not pursue both routes without a careful jurisdictional analysis. Filing another informal protest or an unauthorized second motion may not stop the CTA appeal period.

If the Commissioner denies the protest

A denial by the Commissioner, whether of the original protest or an administrative appeal, may be challenged before the CTA within 30 days from receipt.

A motion for reconsideration filed with the Commissioner after that final denial does not toll the 30-day CTA period under RR No. 18-2013. Waiting for the BIR to act on such a motion can cause the judicial remedy to expire.

CTA litigation is formal court litigation. The petition must comply with the Revised Rules of the Court of Tax Appeals, including rules on verification, certification against forum shopping, parties, annexes, legal representation, filing fees, and service.

What to do if the BIR does not act within 180 days

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

After the 180-day period expires without a decision, the taxpayer has two alternatives:

appeal the inaction to the CTA within 30 days after the 180-day period expires; or
wait for the BIR’s final decision and appeal within 30 days from receipt of that decision.

These remedies are mutually exclusive. Once the taxpayer appeals the inaction, the taxpayer cannot also wait for and pursue a later administrative decision as a separate route. The Supreme Court explained these options in Lascona Land Co., Inc. v. Commissioner of Internal Revenue.

The choice is strategic. An immediate CTA appeal may avoid indefinite administrative delay, while waiting may permit the BIR to resolve the dispute without litigation. Before choosing, verify the correct starting date of the 180-day period and whether the documents submitted were sufficient to start it.

Does protesting stop BIR collection?

A timely protest prevents the disputed assessment from becoming final merely because the taxpayer did nothing. However, do not assume that every administrative or judicial filing automatically suspends all collection activity.

Under Section 11 of Republic Act No. 1125, an appeal to the CTA does not automatically suspend payment or BIR collection. The CTA may suspend collection when collection may jeopardize the interests of the government or the taxpayer, subject to conditions. The court may require a deposit or a surety bond of not more than twice the amount claimed.

If the BIR issues a warrant of distraint or levy, garnishment notice, collection letter, or other enforcement process while the assessment is disputed, obtain tax-litigation advice immediately. A motion to suspend collection requires proper factual support and is not granted automatically.

Evidence to preserve

Preserve both the documents supporting the tax position and the records showing compliance with procedure:

PAN, FLD/FAN, assessment schedules, FDDA, collection notices, and their envelopes;
proof of receipt and delivery for every BIR communication;
letters of authority and audit notices;
tax returns, amended returns, and payment confirmations;
books of accounts, trial balances, general ledgers, and journal entries;
invoices, receipts, contracts, purchase orders, and delivery records;
withholding tax certificates and alphalists;
bank statements and payment records;
import, customs, and excise documents when relevant;
reconciliations between returns, audited financial statements, books, and third-party information;
prior BIR submissions and receiving copies;
email and written communications with BIR personnel;
corporate authority documents; and
working papers showing the BIR’s computation and the taxpayer’s corrected computation.

Keep originals secure. Submit indexed copies unless originals are specifically and lawfully required, and document any turnover of original records.

Common mistakes that can lose the protest

Treating the PAN reply as the final protest

A PAN response ordinarily does not replace the required protest against the FLD/FAN.

Counting from the notice date instead of receipt

The relevant periods generally run from receipt. Preserve objective proof of that date.

Filing a generic objection

A protest must address each disputed issue with facts and legal grounds. Unsupported issues can become final.

Choosing reinvestigation but missing the 60-day document deadline

Later discussions or piecemeal submissions may not cure a missed statutory period.

Filing with the wrong office

A document may be timely prepared but ineffective if not properly filed. Follow the assessment’s instructions and obtain an official received copy.

Relying on verbal extensions

A revenue officer’s assurance ordinarily cannot amend a statutory deadline.

Ignoring an FDDA or collection letter

A new BIR communication may trigger a separate 30-day appeal period. Have it reviewed immediately.

Filing another motion after the Commissioner’s final denial

Such a motion does not suspend the 30-day period for a CTA appeal.

Appealing BIR inaction late

If the taxpayer chooses to appeal after the 180-day period, the petition must be filed within the following 30 days. Otherwise, the taxpayer must consistently follow the alternative route of awaiting the final decision.

Focusing only on the tax principal

Check the statutory basis and computation of surcharge, deficiency interest, delinquency interest, and any compromise penalty separately. A compromise penalty generally rests on agreement; it should not simply be treated as indistinguishable from the assessed tax.

When legal help is urgent

Consult a Philippine tax lawyer immediately when:

fewer than 30 days remain to protest an FLD/FAN;
the date or validity of service is disputed;
the assessment covers several tax types or taxable years;
the assessment may already be final;
the BIR has issued an FDDA, collection letter, warrant of distraint or levy, or garnishment notice;
the 180-day period has expired or is about to expire;
fraud allegations or the extended assessment period are invoked;
officers or employees face possible criminal tax exposure;
the taxpayer is considering a waiver of the statute of limitations;
the BIR assessed withholding taxes or disallowed substantial deductions or input VAT;
the taxpayer intends to pursue compromise or abatement; or
a CTA petition or motion to suspend collection may be necessary.

A request for compromise, abatement, installment payment, or settlement is not automatically a substitute for a timely protest or appeal. Each remedy has separate legal requirements.

Frequently asked questions

Can I protest a Letter of Authority?

A Letter of Authority initiates or defines an audit; it is not ordinarily the final deficiency-tax assessment contemplated by Section 228. Questions about its validity and scope should be raised during the audit and preserved for any PAN or FLD/FAN response.

Can I wait for the BIR to issue a collection letter before protesting?

No. The principal 30-day protest period generally begins upon receipt of the FLD/FAN. Waiting for collection action may allow the assessment to become final.

Must I pay the assessment before filing the protest?

An administrative protest under Section 228 is not generally conditioned on prior payment. Different rules may apply to particular taxes, collection remedies, or requests for judicial suspension, so check the specific assessment.

May I protest only part of the assessment?

Yes, but the undisputed portion may become final, executory, and demandable. Identify precisely what is admitted and what remains contested.

Can the BIR issue an FLD/FAN without a PAN?

Only in the statutory exceptions and other situations permitted by law. If no exception applies, lack of a properly issued and served PAN may be a due-process ground against the assessment.

What if the assessment merely lists amounts without explaining them?

Section 228 requires written notice of the factual and legal bases. Raise the defect expressly and explain why the notice did not permit an intelligent protest. Still file within the 30-day period rather than relying solely on the alleged invalidity.

Can I submit additional documents after 60 days?

For reinvestigation, the required relevant documents must be submitted within 60 days from filing the protest. Do not assume that the BIR’s acceptance of later papers cures noncompliance.

Does an ongoing conference extend the CTA deadline?

Not by itself. Unless a valid rule or court order applies, continue counting the statutory period despite conferences or settlement discussions.

Where can I verify the governing rules?

The central authorities include Section 228 of the National Internal Revenue Code, Revenue Regulations No. 18-2013, Revenue Regulations No. 7-2018, Republic Act No. 1125, and the Revised Rules of the Court of Tax Appeals.

This article provides general legal information, not legal or tax advice for a particular assessment. Deadlines and remedies depend on the exact notices, proof of receipt, issuing authority, protest chosen, documents submitted, and later BIR actions. Primary sources were checked as of August 25, 2026.