Quick answer

To contest a BIR deficiency tax assessment, file a valid written administrative protest within 30 days from receipt of the Formal Letter of Demand and Final Assessment Notice (FLD/FAN). Choose either:

Request for reconsideration — the BIR reevaluates the assessment using the records already available; or
Request for reinvestigation — you will present newly discovered or additional evidence. Submit all supporting documents within 60 days from filing the protest.

A reply to a Notice of Discrepancy or Preliminary Assessment Notice is important, but it does not replace the required protest against the FLD/FAN. Missing the 30-day protest deadline, submitting an invalid protest, or missing the 60-day document deadline for reinvestigation can make the assessment final, executory and demandable.

Act on the document you actually received

BIR audit papers have different legal effects:

Document	What it means	General response period
Letter of Authority or electronic LOA	Identifies the audit authority, covered period and assigned revenue officers	Review immediately
Notice of Discrepancy	Invites discussion and supporting documents; it is not yet a deficiency assessment	Discussion and document submission ordinarily conclude within 30 days from receipt
Preliminary Assessment Notice (PAN)	States the BIR’s proposed assessment	15 days from receipt
FLD/FAN	The formal deficiency assessment and demand for payment	30 days from receipt to protest
Final Decision on Disputed Assessment (FDDA)	Decides the administrative protest	Usually 30 days from receipt for the next remedy
Collection letter, warrant of garnishment, distraint or levy	Indicates actual or imminent collection	Seek professional help immediately

Record the date and manner of receipt of every document. Preserve its envelope, registry notice, courier record, email transmission if any, and the name of the person who accepted it. Service on an accredited tax agent may be treated as service on the taxpayer. Refusing delivery is not a safe way to avoid a deadline.

Before the FLD/FAN: use the early opportunities to correct the record

Notice of Discrepancy

Under the current ordinary audit process, the BIR may first issue a Notice of Discrepancy explaining the audit findings and inviting a Discussion of Discrepancy. This is an opportunity to reconcile third-party data, explain accounting entries and submit missing records before an assessment is proposed. The discussion generally cannot extend beyond 30 days from receipt of the notice.

The notice is not yet a tax assessment, but ignoring it can allow an avoidable factual error to reach the PAN and FLD/FAN stages. Submit a clear reconciliation with indexed evidence and retain a stamped receiving copy.

Preliminary Assessment Notice

A PAN should state the facts and legal grounds for the proposed deficiency. Respond within 15 days from receipt, addressing each tax type and each finding separately.

A PAN is generally required, but Section 228 of the Tax Code allows the BIR to issue an FLD/FAN outright when the deficiency results from:

A mathematical error apparent on the face of the return;
A discrepancy between tax withheld and tax actually remitted;
Carryover of excess creditable withholding tax that was also claimed for refund or tax credit;
Unpaid excise tax on excisable articles; or
Transfer of an exemptly purchased or imported article to a non-exempt person.

A response to the PAN does not eliminate the need for a timely protest if the BIR later issues an FLD/FAN.

Step 1: establish the deadline and protect proof of receipt

Calculate 30 days from the actual date the taxpayer or an authorized recipient received the FLD/FAN. Use calendar days conservatively and file early. If the last day falls during a work suspension, holiday or office closure, confirm the governing rule and any BIR advisory instead of assuming an extension.

Do not wait for:

An informal meeting with the examiner;
A promised revised computation;
A request for documents from another BIR office;
An acknowledgment that the BIR is reviewing the case; or
Approval of a requested extension.

Those events do not ordinarily stop the 30-day period.

Step 2: determine whether the FLD/FAN is complete and valid

Review the entire assessment package, including every annex and computation sheet. Potential objections include both substantive tax issues and defects in the assessment process.

Written factual and legal bases

The FLD/FAN must inform the taxpayer in writing of the facts and the law, regulations or jurisprudence supporting the assessment. A bare amount, unexplained schedule, generic statement or conclusion unsupported by facts may violate Section 228. The Supreme Court treats this requirement as substantive because a taxpayer cannot prepare an effective protest without knowing the case to answer.

Do not rely solely on a procedural defect, however. State it clearly and also answer the assessment on the facts and tax law whenever possible.

Authority to audit

Check the Letter of Authority or electronic LOA for:

The taxpayer’s correct name and TIN;
The taxable period and taxes covered;
The issuing authority;
The names of the assigned revenue officers; and
Any reassignment, consolidation or replacement of the original officers.

Whether a defect in audit authority invalidates an assessment depends on the actual documents and controlling jurisprudence. Preserve every LOA, memorandum of assignment, referral and audit notice for legal review.

Prescription

The general rule under Section 203 of the Tax Code is that an internal revenue tax must be assessed within three years after the last day prescribed for filing the return, or from actual filing if the return was filed late. The period may differ where there is a false or fraudulent return with intent to evade tax, failure to file a return, a valid written waiver, or another statutory ground for suspension or extension.

Prescription is highly document- and date-dependent. Check the return’s due date and filing date, the FLD/FAN issuance and service dates, every waiver, and whether the BIR is invoking fraud or non-filing. Do not simply state that the assessment is “prescribed” without showing the applicable dates and law.

Computation and tax treatment

Recompute the assessment independently. Examine, as applicable:

Whether alleged undeclared sales are actually deposits, transfers, loans, advances, pass-through amounts or reversed transactions;
Whether purchases or expenses were disallowed despite adequate substantiation;
Whether withholding tax credits and prior payments were recognized;
Whether the correct taxable period and tax rate were used;
Whether VAT, percentage tax and income-tax treatments were applied consistently;
Whether penalties and interest were computed under the law applicable to the period; and
Whether the BIR duplicated a transaction or relied on mismatched third-party information.

Under Section 249, the standard interest rate is tied to twice the BSP legal-interest rate; BIR regulations currently reflect a 12% annual standard rate. Deficiency and delinquency interest should not be imposed simultaneously for the same period under the amended rule.

The Ease of Paying Taxes Act also provides reduced civil penalties and a 50% reduction in Section 249 interest for qualifying micro and small taxpayers. Under BIR classification rules, a micro taxpayer generally has annual business gross sales below ₱3 million, while a small taxpayer has at least ₱3 million but below ₱20 million. Confirm the taxpayer’s official classification and whether the concession applies to the particular assessment period.

Step 3: choose the correct protest

The two protest remedies are alternatives. State the choice expressly.

Request for reconsideration

Choose reconsideration when the protest can be decided using records already submitted or already in the audit docket. It may raise factual and legal issues, but it does not contemplate newly discovered or additional evidence.

The special 60-day document-submission period does not apply to reconsideration. Nevertheless, identify the existing documents supporting every argument and attach available copies when useful. Do not label the protest a reconsideration if its success actually depends on evidence not previously available to the BIR.

Request for reinvestigation

Choose reinvestigation when you need to present newly discovered or additional evidence. The protest must identify that evidence, and all relevant supporting documents must be submitted within 60 days from filing the protest.

Do not treat the 60 days as an automatic extension of the 30-day protest deadline. File the protest within 30 days, then complete the evidence submission within the separate 60-day period. After that period, additional documents may be rejected and the assessment may become final as provided in the regulations.

Step 4: prepare an issue-by-issue protest

A valid protest should contain at least:

The taxpayer’s legal name, registered address and TIN;
The tax type and taxable period;
The FLD/FAN date and date of receipt;
An express statement that the filing is a request for reconsideration or request for reinvestigation;
The specific assessment items being disputed;
The material facts for each item;
The applicable statutes, regulations or jurisprudence supporting each objection;
The corrected computation or amount, if any;
For reinvestigation, the newly discovered or additional evidence to be submitted;
A clear request to cancel or modify the disputed assessment;
An indexed list of attachments; and
The taxpayer’s signature or proof that the signatory is authorized to act.

A useful structure is:

Issue 1: Description of assessment
BIR position
Relevant facts
Taxpayer’s legal position
Evidence
Correct computation
Relief requested

Address every disputed item. If the FLD/FAN contains several issues but the protest challenges only some of them—or gives no factual and legal support for others—the unchallenged items may become final, executory and demandable.

The Supreme Court has upheld strict application of these formal requirements. A letter that merely says the taxpayer disagrees, requests more time, or asks for a conference may not constitute a valid protest.

Step 5: file with the correct BIR office

BIR guidance directs the initial protest to the duly authorized representative who signed the FLD/FAN. Confirm the receiving office shown in the notice, particularly where the audit has been transferred, consolidated or handled by the Large Taxpayers Service or National Office.

Use an officially accepted filing method. Obtain reliable proof showing:

The date of filing;
The receiving office;
The name or stamp of the receiving officer;
The number of pages and attachments; and
The identity of the taxpayer and assessment.

For personal filing, obtain a stamped copy. For an authorized mailing or courier method, preserve the receipt, tracking record and complete filed set. Do not assume ordinary email or an eAFS upload is valid for an assessment protest unless a specific BIR issuance or written office instruction authorizes that channel.

If a representative files or signs, include the appropriate authorization, such as a special power of attorney, secretary’s certificate, board authorization or other evidence suited to the taxpayer.

Step 6: submit and preserve the evidence

For a reinvestigation, submit all relevant documents within the 60-day period and secure proof of filing. Consider including:

Tax returns, amendments and electronic filing confirmations;
Audited financial statements and tax-reconciliation schedules;
General and subsidiary ledgers;
Sales and purchase invoices;
Official payment records;
Withholding tax certificates and alphalists;
Bank statements and deposit reconciliations;
Contracts, purchase orders and delivery documents;
Loan, advance and intercompany-account records;
Importation and customs records;
Payroll records;
Prior BIR rulings or written confirmations relevant to the transaction;
Correspondence with customers, suppliers and the BIR; and
A schedule connecting each document to a specific protest issue.

Keep an exact electronic and physical copy of everything filed. Preserve original records and metadata; do not alter, backdate or reconstruct evidence without clearly identifying it as a later-prepared reconciliation.

Step 7: monitor the 180-day decision period

For a request for reconsideration, the 180-day period is generally counted from filing of the protest. For a request for reinvestigation, it is generally counted from submission of the required supporting documents within the 60-day period. Because disputes can arise over the correct starting date, keep a written deadline chart and all receiving records.

If the BIR issues an FDDA before the 180 days expire, the next deadline ordinarily runs from receipt of that decision.

If there is no action within 180 days, the taxpayer generally has two mutually exclusive choices:

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

Do not let the first option’s 30-day window pass accidentally. Deciding whether to appeal inaction or wait requires an assessment of collection risk, the completeness of the record and the likely benefit of further administrative review.

Step 8: respond correctly to the FDDA

Read the dispositive portion and identify who signed the decision.

If an authorized representative of the Commissioner denied the protest, the taxpayer generally has 30 days from receipt to choose between:

Appealing directly to the CTA; or
Elevating the matter to the Commissioner through a request for reconsideration.

A reinvestigation is no longer available at this stage, and the administrative appeal is limited to issues addressed in the representative’s decision.

If the Commissioner personally denies the protest or administrative appeal, the remedy is generally an appeal to the CTA within 30 days from receipt. Filing another motion for reconsideration with the Commissioner does not stop the CTA appeal period.

During the current BIR National Office energy-conservation arrangement, RMC No. 35-2026 provides that a Friday deadline for filing a request for reconsideration of an FDDA at the National Office moves to the next business day when personnel work on-site. This limited rule does not change CTA deadlines; verify that the underlying work arrangement remains effective.

Appealing to the Court of Tax Appeals

A CTA appeal is court litigation, not another informal BIR letter. It normally requires a verified petition for review, payment of docket and lawful fees, proper service, supporting documents and compliance with the Revised Rules of the Court of Tax Appeals and its latest filing resolutions.

The rules allow a motion for a limited extension in appropriate circumstances, but relying on an extension is risky. Engage tax counsel before the original 30-day period expires.

An administrative protest or CTA appeal does not automatically suspend tax collection. Under Section 11 of Republic Act No. 1125, as amended, the CTA may suspend collection when warranted and may require a deposit or surety bond of not more than twice the amount claimed. If the BIR has issued a warrant, garnished an account, levied property or threatened a sale, urgent court relief may be necessary.

Evidence and records to preserve immediately

Keep a secure assessment file containing:

Every BIR notice, annex and computation;
Envelopes, registry cards, courier records and proofs of receipt;
The LOA or electronic LOA and all assignment documents;
Notes of meetings and calls, including attendees and dates;
All submissions with stamped receiving copies;
Tax returns, filing confirmations and payment records;
Accounting records and source documents;
Proof of the taxpayer’s registered address and any registration updates;
Authorization documents for representatives; and
A deadline calendar for the 15-, 30-, 60- and 180-day periods.

Common and costly mistakes

Treating a PAN response as the required FLD/FAN protest;
Filing a vague objection without choosing reconsideration or reinvestigation;
Omitting the assessment date, legal grounds or material facts;
Challenging only the total amount instead of every assessment item;
Choosing reconsideration while depending on new evidence;
Missing the 60-day evidence deadline for reinvestigation;
Filing with the examiner instead of the proper authorized office;
Failing to obtain proof of filing;
Assuming ongoing negotiations extend a deadline;
Ignoring service at the taxpayer’s registered address or on its tax agent;
Filing another motion with the Commissioner and assuming it stops the CTA period;
Appealing BIR inaction late; and
Assuming that a protest automatically stops interest or collection.

When professional help is urgent

Consult a Philippine tax lawyer promptly when:

Fewer than 10 days remain before a protest or appeal deadline;
The assessment involves fraud, a false return or possible criminal exposure;
The BIR invokes the 10-year assessment period;
The taxpayer signed waivers extending the assessment period;
The assessment concerns several tax types or taxable years;
The authority of the audit officers is disputed;
The FLD/FAN or FDDA lacks clear factual and legal bases;
A collection letter, garnishment, distraint or levy has been issued;
The taxpayer must decide whether to appeal BIR inaction;
The FDDA was signed by the Commissioner; or
A CTA petition or suspension of collection is being considered.

A CPA can help reconstruct transactions and computations, but CTA litigation and legal validity issues should be coordinated with qualified tax counsel.

Frequently asked questions

Must I pay the full assessment before protesting?

Generally, no prepayment is required merely to file a timely administrative protest. Any undisputed portion may become immediately collectible, however, and interest and collection risks must be evaluated separately.

Can I protest only part of the assessment?

Yes, but identify every disputed item precisely. An undisputed or unsupported item may become final and demandable.

Can the BIR extend the 30-day protest period?

Do not assume so. Treat the 30-day period as mandatory and file a complete, valid protest within it.

What if I need documents that are still with a customer or bank?

If additional evidence is necessary, consider a request for reinvestigation and identify the evidence in the timely protest. All relevant supporting documents must still be submitted within 60 days from filing.

What if the BIR calls its letter something other than an FDDA?

Substance can matter more than the label. A letter that clearly denies the protest and demands payment may trigger an appeal deadline. Obtain legal advice immediately rather than waiting for another document.

Can I ignore an assessment sent to my old address?

No. BIR notices may be served at the registered or known address, and failure to update registration can create serious receipt and deadline problems. Preserve the delivery evidence and obtain advice on whether service was legally effective.

Does this procedure apply to city or municipal taxes?

No. Local business and real-property tax disputes follow different procedures under the Local Government Code and local ordinances.

Can I apply for compromise instead of protesting?

A compromise under Section 204 may be available in qualifying cases involving doubtful validity or financial incapacity, subject to statutory standards and approval. It is not an automatic right and should not be assumed to suspend the protest or appeal deadlines.

Official legal references

This article provides general legal information, not legal or tax advice for a particular assessment. Results depend on the notices, audit authority, taxable period, evidence, service records and procedural history. Philippine law and BIR procedures were checked against official sources through July 23, 2026.