Quick answer

You may contest a Bureau of Internal Revenue assessment by filing a valid written protest against the Formal Letter of Demand and Final Assessment Notice (FLD/FAN) within 30 days from receipt. Choose either:

A request for reconsideration, based only on records already available to the BIR; or
A request for reinvestigation, based on newly discovered or additional evidence. For this remedy, all relevant supporting documents must be submitted within 60 days from filing the protest.

Missing the 30-day protest deadline will generally make the assessment final, executory, and demandable. A vague reservation such as “we disagree and will submit details later” may not qualify as a valid protest. Section 228 of the National Internal Revenue Code and its implementing regulations require specific factual and legal grounds. National Internal Revenue Code, Section 228 and Revenue Regulations No. 18-2013.

Know which BIR notice you received

Different notices trigger different remedies and deadlines.

Document	What it means	Usual response
Notice of Discrepancy or similar audit correspondence	The BIR is still investigating	Attend or respond as directed; reconcile the discrepancies and submit evidence
Preliminary Assessment Notice (PAN)	A proposed deficiency assessment	Submit a written reply, ordinarily within 15 days from receipt
FLD/FAN	The formal assessment and demand for payment	File a valid protest within 30 days from receipt
Final Decision on Disputed Assessment (FDDA)	The BIR’s decision on the protest	Appeal administratively or to the Court of Tax Appeals, as applicable, within 30 days from receipt
Collection letter, warrant of distraint or levy, or garnishment notice	The BIR is pursuing collection	Obtain urgent legal advice; determine whether the document is also a final decision that starts a CTA deadline

A reply to a PAN is useful but is not the same as the formal protest against an FLD/FAN. Under BIR rules, a PAN reply is generally optional in the sense that failure to file it does not remove the taxpayer’s right to protest a later FLD/FAN. Still, responding is strongly advisable because it may correct the assessment before it becomes formal and creates a record that the BIR must consider. Revenue Memorandum Order No. 26-2016.

When the BIR may issue an assessment without a PAN

A PAN is normally required. Section 228 permits the BIR to issue an FLD/FAN directly when:

The deficiency results from a mathematical error appearing on the face of the return;
There is a discrepancy between tax withheld and the amount remitted by the withholding agent;
A taxpayer both claimed a refund or tax credit for excess creditable withholding tax and carried over 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 sold, traded, or transferred to a non-exempt person.

Outside these exceptions, failure to issue and properly serve a PAN may violate due process. Even when no PAN is required, the FLD/FAN must still state the factual and legal bases of the assessment.

Record the date and manner of receipt immediately

The critical periods generally run from receipt, not from the date printed on the notice. On the day a notice arrives:

Scan the complete notice, schedules, attachments, envelope, registry return card, courier pouch, and transmittal documents.
Record the date, time, place, delivery method, and identity and position of the person who accepted it.
Preserve office receiving logs, security logs, emails, text messages, and courier tracking records.
Check whether a copy was also received by an accredited tax agent or authorized representative. Service on an appointed tax agent may be treated as service on the taxpayer.
Update the company’s BIR registration promptly if its registered address has changed.

BIR notices may be served personally, by substituted service, by registered or ordinary mail in the circumstances allowed by the regulations, or through a reputable courier. Delivery at the taxpayer’s registered address to an appropriate person may be effective even if senior management learns about it later. Revenue Regulations No. 18-2013.

If actual receipt is genuinely disputed, preserve the original records. The Supreme Court has required the BIR to prove proper receipt when the taxpayer directly denies receiving the assessment, but this is a fact- and evidence-dependent defense—not a reason to ignore a notice that was actually received. CIR v. Villanueva, G.R. No. 249540.

Choose the correct type of protest

Request for reconsideration

Use reconsideration when the assessment can be resolved from records already submitted or available to the BIR. Typical issues include:

A computational error;
Incorrect application of a tax rate;
Double counting;
Failure to credit a payment or withholding certificate already on record;
An incorrect legal interpretation; or
A procedural defect apparent from the audit record.

The 60-day period for submitting additional evidence does not apply to reconsideration because the remedy is based on existing records. Documents needed to establish the grounds should nevertheless be organized and identified in the protest itself.

Request for reinvestigation

Use reinvestigation when you need the BIR to consider newly discovered or additional evidence, such as contracts, invoices, reconciliations, payment records, accounting schedules, bank records, or third-party confirmations not previously submitted.

The protest must identify the additional evidence you intend to present. All relevant supporting documents must be submitted within 60 days from filing the protest. Evaluation is generally limited to documents submitted within that period.

A protest is treated as a request for reconsideration unless it clearly states that it is a request for reinvestigation. You cannot pursue both remedies for the same disputed assessment.

The distinction may also affect prescription for collection. A request for reinvestigation that the BIR grants can suspend the applicable collection period; merely filing the request is not enough. A reconsideration generally does not have that statutory effect. BPI v. CIR, G.R. No. 139736.

What a valid protest should contain

Prepare the protest issue by issue. It should include at least:

The taxpayer’s complete name, TIN, registered address, and contact information;
The tax type and taxable period involved;
The FLD/FAN number, assessment date, date of receipt, and amount assessed;
An express statement that the letter is a protest under Section 228;
A clear choice between reconsideration and reinvestigation;
For reinvestigation, a description of the newly discovered or additional evidence to be submitted;
Every factual ground for disputing each assessment item;
The applicable statutes, regulations, or jurisprudence supporting each ground;
Corrected computations and reconciliation schedules;
An attachment index linking each document to the issue it proves;
A specific request to cancel or reduce the assessment; and
The taxpayer’s or authorized representative’s signature, with proof of authority when appropriate.

Address every tax type, taxable period, adjustment, and penalty you intend to dispute. If the protest challenges only some issues, the unchallenged portions may become final and collectible. The same result may follow when an issue is mentioned but no factual and legal basis is provided.

Pay any portion that you expressly accept, using the applicable BIR payment procedure, while clearly identifying the remaining disputed portion. Payment and settlement discussions should never be assumed to extend a protest or appeal deadline.

Where and how to file

File the protest with the duly authorized BIR representative who signed the PAN and FLD/FAN, following the filing instructions in the assessment. BIR guidance directs taxpayers to file with the proper signatory office; an administrative appeal from that representative’s decision is filed with the Office of the Commissioner. Revenue Memorandum Circular No. 11-2014.

Before the deadline:

Confirm the exact receiving office and its current filing instructions.
Use the filing method stated in the notice or officially authorized by the BIR.
If filing personally, obtain a stamped receiving copy showing the date, time, office, receiver, and number of pages or attachments.
If an authorized mailing method is used, retain the original registry or courier receipt, tracking history, envelope, return card, and complete duplicate of the submission.
Do not assume that ordinary email, a phone call, an informal meeting, or delivery to the examining revenue officer constitutes valid filing.
Keep both an unaltered electronic copy and a bound physical duplicate.

The 30-day deadline should be treated as firm. Do not rely on an oral extension. A special extension applies only when a valid law or BIR issuance expressly covers the taxpayer, document, location, and due date.

As of the source-check date, RMC No. 35-2026 provides a narrow rule for a request for reconsideration of an FDDA filed at the BIR National Office: if its due date falls on a Friday while the cited energy-conservation work arrangement remains effective, filing moves to the next business day when National Office personnel work on-site. This does not generally extend an initial FLD/FAN protest or a CTA deadline.

Build the evidence file

Preserve and organize:

The Letter of Authority and any amended or replacement authority;
All BIR notices, demand letters, schedules, and attachments;
Proof of receipt and service for every notice;
Tax returns, audited financial statements, trial balances, ledgers, and journal entries;
Invoices, withholding certificates, proof of payment, contracts, delivery records, and bank documents;
Reconciliations between returns, financial statements, and third-party information;
Prior submissions to the BIR and proof that each was received;
Meeting minutes, written explanations, and correspondence with revenue officers;
Corporate authorizations, powers of attorney, and tax-agent accreditation records; and
A deadline chart covering the PAN, FLD/FAN, supporting documents, BIR decision period, and CTA appeal.

Avoid altering original files. Preserve metadata and explain genuine discrepancies through a reconciliation instead of creating replacement records.

Review both the numbers and the validity of the assessment

Possible grounds depend on the documents and facts. Common areas for review include:

Factual and computational errors

Check for duplicated sales, incorrect tax bases, uncredited withholding taxes or payments, disallowed expenses that are adequately supported, incorrect periods, and arithmetic errors. Submit a line-by-line reconciliation rather than a bare denial.

Wrong legal treatment

Determine whether the transaction was taxable, exempt, zero-rated, subject to withholding, deductible, or governed by a special law or treaty. Apply the law in force during the assessed taxable period, not merely the current rule.

Failure to state factual and legal bases

The PAN, FLD/FAN, and FDDA must inform the taxpayer of the facts and law supporting the assessment or decision. A computation accompanied only by unexplained statutory citations may be insufficient. The BIR must also genuinely consider the taxpayer’s explanations and evidence. CIR v. Yumex Philippines Corp., G.R. No. 222476.

Defective audit authority

Confirm that the revenue officers who examined the books were properly named and authorized by a valid Letter of Authority. The Supreme Court has ruled that substituting officers through a mere memorandum, without the required separate or amended authority, can violate due process and invalidate the resulting assessment. Application of this doctrine depends on the audit documents. CIR v. McDonald’s Philippines Realty Corp., G.R. No. 242670.

Prescription

The ordinary period for assessment is generally three years from the statutory filing deadline or actual filing of the return, whichever is later. Exceptions—including failure to file, a fraudulent return with intent to evade tax, and a valid written waiver—require separate analysis under Sections 203 and 222. Examine the actual return dates, assessment release and service records, waivers, and alleged fraud; do not rely only on the date printed on the FAN.

What happens during the BIR’s 180-day decision period

For a reconsideration, the 180-day period is generally counted from filing the protest. For a reinvestigation, it is counted from submission of the required supporting documents within the 60-day period.

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

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

Once the taxpayer chooses to appeal the inaction, the taxpayer cannot later switch to waiting for an administrative decision. An appeal filed after the 30-day window for challenging inaction cannot be rescued by later claiming the second option. Mannasoft Technology Corp. v. CIR, G.R. No. 244202.

Maintain a written computation of both the 60-day and 180-day periods. Disputes often arise over the date when the complete supporting documents were submitted.

Responding to an FDDA

An FDDA must state its factual and legal bases and indicate that it is the BIR’s final decision.

If the FDDA was issued by the Commissioner’s duly authorized representative, the taxpayer generally has 30 days from receipt to choose between:

Filing a petition for review with the CTA; or
Elevating the matter to the Commissioner through a request for reconsideration.

A reinvestigation is no longer available at this stage. The administrative appeal is limited to matters covered by the representative’s decision.

If the Commissioner denies the protest or administrative appeal, the remedy is generally a CTA petition within 30 days from receipt. Filing another motion for reconsideration with the Commissioner does not suspend or restart that CTA deadline.

The substance of a communication matters more than its label. A collection letter, demand, or warrant that clearly rejects the protest and demands payment may, in some circumstances, be treated as the appealable final decision. Have such a document reviewed immediately.

Appealing to the Court of Tax Appeals

The judicial remedy is a petition for review before a CTA Division under the Revised Rules of the Court of Tax Appeals. The statutory period is normally 30 days from:

Receipt of the appealable final decision; or
Expiration of the BIR’s 180-day period, if the taxpayer chooses to appeal the inaction.

The CTA is a court of special jurisdiction. A premature petition, an appeal filed after the applicable deadline, or an appeal based on an invalid administrative protest may be dismissed without a ruling on the correctness of the assessment. See the Revised Rules of the Court of Tax Appeals and Republic Act No. 9282.

An appeal to the CTA does not automatically suspend payment, distraint, levy, garnishment, or sale of property. The CTA may suspend collection when the legal standard is met and may require a deposit or surety bond of up to twice the amount claimed. A request to suspend collection requires prompt preparation and supporting evidence.

Common mistakes to avoid

Counting from the day management opened the notice instead of the legally relevant receipt date;
Treating a PAN reply as the protest against the FLD/FAN;
Filing only a reservation to submit a detailed protest later;
Failing to choose reconsideration or reinvestigation;
Calling the protest a reinvestigation without identifying additional evidence;
Omitting factual and legal grounds for individual assessment items;
Missing the 60-day document deadline;
Submitting documents without an index or explanation of what each proves;
Filing with the examining officer instead of the proper signatory office;
Relying on an email or oral assurance without formal proof of filing;
Assuming settlement talks stop the deadline;
Failing to pay or expressly address undisputed portions;
Missing the 180-day inaction calendar;
Filing another BIR motion and assuming it extends the CTA deadline; or
Assuming that a CTA appeal automatically stops collection.

When legal help is urgent

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

Fewer than 10 days remain before a protest or CTA deadline;
The assessment is large relative to the taxpayer’s assets or cash flow;
Fraud, willful non-filing, substantial underdeclaration, or possible criminal liability is alleged;
The BIR has issued a collection letter, garnishment, warrant of distraint or levy, or seizure notice;
The business risks closure or loss of essential property;
Receipt or service of the assessment is disputed;
The audit involved officers not named in the Letter of Authority;
Prescription or a waiver of the assessment period is in issue;
The FDDA is unclear, unsigned by the proper official, or lacks factual and legal bases; or
The taxpayer must decide whether to appeal BIR inaction or await a decision.

Frequently asked questions

Do I have to pay the disputed assessment before filing a protest?

Generally, no. A timely administrative protest may be filed without first paying the disputed amount. Any portion accepted or left undisputed should be addressed and paid through the proper BIR procedure. Collection risk becomes more serious after finality and during judicial appeal because a CTA petition does not automatically suspend collection.

Can I submit a short protest now and provide the grounds later?

Do not rely on that approach. The protest itself must identify the remedy, assessment, issues, and supporting factual and legal bases. A letter merely stating that the taxpayer disagrees or is still gathering documents may be invalid.

Can I submit documents after the 60-day period?

For reinvestigation, the BIR generally evaluates only documents submitted within the 60-day period. Late evidence may be rejected, and failure to submit relevant documents may cause the assessment to become final. File early and obtain proof identifying the documents delivered.

What if I never received the FAN?

Verify the BIR’s service records, the taxpayer’s registered address, mail and courier records, and whether an authorized representative received it. A direct denial of receipt can require the BIR to prove proper service, but substituted service and service at the registered address may be valid.

Is a BIR email a valid assessment?

Validity depends on the document, issuing authority, applicable service rules, and proof of receipt. Do not ignore an electronic communication. Preserve it, verify it directly with the proper BIR office using official contact details, and have it reviewed before any apparent deadline.

Can the 30-day period be extended?

Assume it cannot unless a specific, valid issuance or court rule unquestionably applies and all its requirements are met. Oral assurances do not extend the statutory period. The narrow National Office Friday rule under RMC No. 35-2026 applies only to the circumstances stated in that circular.

What if the BIR does nothing for 180 days?

You may appeal the inaction to the CTA within the next 30 days or continue waiting for a final decision. These options are mutually exclusive. The better choice depends on collection risk, the completeness of the record, and the case strategy.

Can the BIR collect while the CTA case is pending?

Yes, collection is not automatically suspended by the appeal. The taxpayer may ask the CTA to suspend collection, subject to the statutory standard and possible deposit or bond.

Official references

This article provides general legal information, not legal or tax advice. The correct remedy may depend on the actual assessment, service records, audit authority, evidence, taxable period, and current BIR issuances. Sources and procedures were checked as of August 3, 2026.