Quick answer

If you receive a BIR Formal Letter of Demand and Final Assessment Notice (FLD/FAN) and disagree with it, you generally have 30 days from receipt to file a valid written administrative protest. The protest must be either a request for reconsideration or a request for reinvestigation, must identify the assessment being challenged, and must state the legal and factual basis for contesting the assessment. Missing the 30-day deadline can make the assessment final, executory, and demandable.

If you choose reinvestigation because you need to present newly discovered or additional evidence, you must submit the relevant supporting documents within 60 days from filing the protest. That 60-day documentary period does not apply to a request for reconsideration, which asks the BIR to reevaluate the assessment using the existing record.

After a valid protest, another critical period is 180 days. Depending on who is acting and which protest route you chose, the BIR's inaction may allow you to appeal to the Court of Tax Appeals (CTA). If the applicable 180-day period expires without a decision, you generally have two mutually exclusive choices: appeal the inaction to the CTA within the following 30 days, or continue waiting for the BIR's final decision and then appeal that decision within 30 days from receipt.

These deadlines are jurisdictionally important. Do not treat a BIR assessment protest as an ordinary letter asking the examiner to reconsider.

First determine what BIR document you received

The appropriate response depends on the stage of the assessment.

Notice of Discrepancy or audit findings

During an audit, the BIR may communicate discrepancies before issuing a formal assessment. This is an opportunity to explain reconciliations, produce documents, and contest proposed adjustments early. It is not yet the Section 228 protest against a final assessment. BIR guidance provides for discussion of discrepancies before the case proceeds to the reviewing office for assessment.

Preliminary Assessment Notice

A Preliminary Assessment Notice (PAN) ordinarily precedes the FLD/FAN. Under Revenue Regulations No. 18-2013, the taxpayer normally has 15 days from receipt of the PAN to respond. The PAN should state in detail the facts and the law, rules, regulations, or jurisprudence supporting the proposed deficiency.

Responding to the PAN is important, but a PAN response is not a substitute for protesting the later FLD/FAN. If the BIR subsequently issues an FLD/FAN, calculate a new and separate 30-day protest deadline from receipt of that final assessment.

There are also statutory situations where the BIR may issue an FLD/FAN without first issuing a PAN, including certain mathematical errors appearing on the face of a return, discrepancies between tax withheld and tax actually remitted, specified excess-creditable-withholding-tax situations, unpaid excise taxes, and transfers of certain articles from exempt to non-exempt persons. (Lawphil)

Formal Letter of Demand and Final Assessment Notice

The FLD/FAN is the document that normally triggers the 30-day period for filing the administrative protest.

The assessment must state the facts and the law, rules, regulations, or jurisprudence upon which it is based. Section 228 of the Tax Code and RR No. 18-2013 provide that failure to adequately state the legal and factual basis can render an assessment void. (Lawphil)

Do not assume, however, that an apparent defect allows you to ignore the FLD/FAN. Preserve the objection and file the protest within the applicable deadline.

The critical deadlines at a glance

Event	General deadline
Response to PAN	15 days from receipt
Protest against FLD/FAN	30 days from receipt
Additional documents for request for reinvestigation	60 days from filing the protest
BIR action period on reconsideration before an authorized representative	180 days from filing the protest
BIR action period on reinvestigation before an authorized representative	180 days from submission of the required supporting documents within the 60-day period
Appeal from adverse FDDA issued by authorized representative	Generally 30 days from receipt, either to CTA or administratively to the CIR
CTA appeal based on BIR inaction	30 days after expiration of the applicable 180-day period
CTA appeal after waiting for a later final decision	30 days from receipt of that final decision

The exact computation can change depending on whether the protest is reconsideration or reinvestigation, whether the decision came from the Commissioner's authorized representative or the Commissioner personally, and whether the taxpayer elects administrative review or CTA review.

Step 1: Record the exact date and manner of receipt

The first task is not drafting arguments. It is establishing when the countdown started.

Keep the original:

FLD/FAN and all attachments;
envelope and registered-mail markings;
registry notice or postal records;
receiving stamp;
courier or personal-service documentation;
documents showing who received the notice and where it was served; and
PAN, responses, audit notices, and earlier correspondence.

Service can itself become an important issue. The Supreme Court has stressed that BIR assessment notices must be properly served and that the government bears the burden of establishing proper service when it relies on substituted service. Improper service may materially affect whether an assessment became final and when periods began to run. (Lawphil)

Never discard the envelope merely because you already have a copy of the assessment.

Step 2: Decide between reconsideration and reinvestigation

Your protest must identify which remedy you are choosing.

Request for reconsideration

A request for reconsideration asks the BIR to reevaluate the assessment on the basis of the existing record, without additional evidence. It can raise questions of fact, law, or both.

This is generally appropriate when the documents necessary to resolve the assessment are already part of the BIR record and the dispute concerns matters such as:

an incorrect interpretation of the Tax Code;
improper application of a regulation;
a mathematical or computational error;
a legal characterization of a transaction; or
evidence already submitted during the audit.

The special 60-day supporting-document deadline applicable to reinvestigation does not apply to reconsideration.

Request for reinvestigation

A request for reinvestigation asks for reevaluation using newly discovered or additional evidence that you intend to submit.

This may be necessary where the assessment can be rebutted only by materials that were not previously included in the audit record—for example, additional invoices, reconciliations, withholding certificates, contracts, accounting schedules, bank records, or other substantiating evidence.

If you choose reinvestigation, identify the additional evidence in the protest and submit all relevant supporting documents within 60 days from filing the protest. Failure to comply can cause serious consequences, including the assessment becoming final as contemplated by the applicable regulations and the loss of the opportunity to dispute it through additional evidence.

Choose carefully. BIR rules treat reconsideration and reinvestigation as distinct remedies.

Step 3: Make the protest valid on its face

A bare statement such as "We disagree with the assessment and request reconsideration" is dangerous.

RR No. 18-2013 requires the protest to state, among other things:

whether it is a request for reconsideration or reinvestigation;
if reinvestigation, the newly discovered or additional evidence intended to be presented;
the date of the assessment notice; and
the applicable law, rules, regulations, or jurisprudence upon which the protest is based.

For every adjustment you intend to contest, explain the material facts and the legal basis for the objection.

This matters because where an FLD/FAN contains several separate issues and the taxpayer contests only some of them, the assessment attributable to the undisputed issues may become final, executory, and demandable. The same problem can arise where an issue is nominally mentioned but the taxpayer fails to state facts and legal grounds supporting the challenge to that issue.

A careful protest therefore normally deals with the assessment issue by issue and tax type by tax type.

Step 4: Build the supporting record

Before finalizing the protest, reconcile the FLD/FAN against the underlying audit working papers and the taxpayer's own records.

Depending on the assessment, potentially important evidence includes tax returns and amendments, audited financial statements, trial balances and general ledgers, sales and purchase registers, invoices, withholding-tax certificates, payroll records, contracts, bank records, import documents, proofs of payment, schedules previously furnished to the BIR, and correspondence exchanged during the audit.

Also preserve evidence supporting procedural objections, such as the Letter of Authority and any amendments or reassignment documents, PAN and proof of service, FLD/FAN and proof of service, Details of Discrepancies, notices issued during the audit, and copies of every submission to the BIR with proof of filing.

Do not merely collect documents. Tie each document to the particular factual assertion or adjustment it disproves.

Step 5: File the protest with the correct BIR office

BIR guidance instructs taxpayers to address the protest to the Assistant Commissioner, Regional Director, or other authorized higher revenue official concerned and file it with the office that issued the FLD/FAN for recording and evaluation.

Revenue Memorandum Circular No. 15-2020 states that an administrative protest may be:

filed in person; or
sent through registered mail to the appropriate office.

For registered mail, BIR guidance states that the date of mailing shown by the post-office stamp on the envelope is treated as the filing date, and the envelope forms part of the case docket.

If filing personally, obtain a properly dated receiving copy. If using registered mail, retain the registry receipt, tracking records, complete copy of what was mailed, and other proof showing timely dispatch.

Do not rely casually on an unconfirmed email transmission or informal delivery to the handling examiner when the regulations prescribe formal filing with the proper office.

Step 6: Track the 60-day and 180-day periods separately

If your protest is a reinvestigation, calendar the 60-day supporting-document deadline immediately. Do not wait for the BIR to remind you.

Then calendar the applicable 180-day period.

For a protest filed with the Commissioner's duly authorized representative, RR No. 18-2013 provides that the 180 days are generally counted:

from the filing of the protest for a request for reconsideration; or
from the submission of the required documents, made within the 60-day period, for a request for reinvestigation.

The precise starting date can determine CTA jurisdiction. Maintain a written deadline schedule rather than relying on memory.

If the BIR denies the protest

The BIR normally communicates its resolution through a Final Decision on Disputed Assessment (FDDA).

An FDDA must state the facts and applicable law, rules, regulations, or jurisprudence supporting the decision and must indicate that it is the final decision.

If the FDDA was issued by the Commissioner's duly authorized representative and denies the protest wholly or partly, RR No. 18-2013 gives the taxpayer two principal choices within 30 days from receipt:

appeal directly to the Court of Tax Appeals; or
elevate the matter administratively to the Commissioner of Internal Revenue through a request for reconsideration.

At this administrative-appeal stage, a new request for reinvestigation is not permitted. The regulations provide for reconsideration, and only the issues addressed in the authorized representative's decision are entertained by the Commissioner.

If the Commissioner thereafter denies the protest or administrative appeal, the taxpayer generally has 30 days from receipt of the Commissioner's decision to appeal to the CTA. Filing another motion for reconsideration with the Commissioner does not suspend or restart that CTA appeal period.

If the BIR does nothing for 180 days

BIR inaction does not mean that the assessment disappears.

After expiration of the applicable 180-day period, the taxpayer may generally choose between two routes:

Appeal the inaction

The taxpayer may file a petition for review with the CTA within 30 days after expiration of the 180-day period.

Wait for the BIR's final decision

Instead of appealing the inaction, the taxpayer may wait for a formal decision and then appeal that final decision to the CTA within 30 days after receiving it.

The Supreme Court has repeatedly recognized these two alternatives. They are mutually exclusive: once the taxpayer chooses the appeal-from-inaction route, that choice bars use of the waiting-for-a-final-decision route for the same inaction. (Lawphil)

This election is consequential. Get the 180-day computation and litigation strategy settled before the deadline expires.

Appealing to the Court of Tax Appeals

The CTA has appellate jurisdiction over decisions and qualifying inaction of the Commissioner involving disputed assessments. The appeal is made by petition for review in accordance with the CTA Rules. (Lawphil)

The basic 30-day periods are strict. A petition filed late can leave the assessment final regardless of the strength of the underlying tax arguments.

A taxpayer appealing an FDDA should also be aware of Revenue Memorandum Circular No. 43-2023. It requires a taxpayer filing an appeal against an FDDA with the Office of the Commissioner or the CTA to furnish a copy of the appeal, within five days from filing, to the Chief of the Assessment Division for regional cases or to the specified responsible office for Large Taxpayers Service or National Investigation Division cases. (BIR)

Current 2026 Friday-deadline rule for certain National Office reconsiderations

There is a narrow current operational rule worth noting.

Revenue Memorandum Circular No. 35-2026 provides that, while Revenue Memorandum Order No. 007-2026 remains in effect, a request for reconsideration of an FDDA within the National Office whose due date falls on a Friday has its filing deadline moved to the next business day when National Office personnel are working on-site. The circular was issued in connection with the BIR's 2026 energy-conservation work arrangements.

Do not automatically apply that accommodation to an initial FLD/FAN protest, to other filings, or to a CTA deadline. Its wording is specific. When a deadline is close, verify the current BIR issuance and actual government work schedule instead of assuming an extension.

Potential grounds for contesting an assessment

The proper grounds depend entirely on the audit record and tax involved. Common areas requiring review include factual or computational errors, incorrect application of tax law or regulations, transactions incorrectly characterized by the BIR, deductions or input taxes allegedly unsupported despite available substantiation, withholding-tax reconciliations, assessments issued beyond an applicable prescriptive period, procedural due-process defects, improper service of assessment notices, and questions concerning the authority under which the examination was conducted.

An assessment should not be attacked with boilerplate objections. A strong protest connects the specific adjustment, the relevant facts, the evidence, and the controlling legal rule.

Procedural defects can sometimes be decisive, but not every irregularity automatically voids an assessment. For example, RR No. 18-2013 itself provides that an FLD/FAN issued more than 15 days after a taxpayer's PAN response is not invalid for that reason alone if it was still issued within the applicable period for assessment. (BIR)

What if you agree with only part of the assessment?

You may dispute only part of an FLD/FAN, but do so consciously.

BIR rules state that the portion attributable to issues not disputed can become final, executory, and demandable. BIR administrative guidance likewise contemplates paying the accepted portion while continuing to contest the balance.

Accordingly, the protest should expressly identify which assessments and adjustments are contested and which, if any, are accepted.

Common mistakes that can destroy an otherwise valid defense

Missing the FLD/FAN protest deadline

The usual 30-day period runs from receipt of the FLD/FAN. A good explanation filed on day 31 may not cure the failure to file a timely valid protest.

Thinking the PAN response was enough

The PAN response and FLD/FAN protest are separate procedural stages.

Calling a protest "reconsideration" while planning to rely on new evidence

The regulations distinguish reconsideration from reinvestigation. Choose the remedy that matches how you intend to prove the case.

Choosing reinvestigation and missing the 60-day document deadline

This can result in the loss of the opportunity to contest the assessment through additional evidence.

Contesting only the total amount

Address each tax type and adjustment. An issue that is not properly disputed can become final even when other portions remain contested.

Filing with the wrong office or keeping no proof of filing

A protest is deadline-driven. Preserve a received copy or registered-mail evidence.

Miscomputing the 180-day period

For reconsideration and reinvestigation, the starting points are different.

Waiting after an FDDA because the BIR is still communicating with you

Once an appealable final decision has been received, informal discussions generally should not be assumed to suspend the statutory CTA period. The Supreme Court has repeatedly treated receipt of a final decision as critical to the 30-day appeal period. (Lawphil)

Filing another motion with the Commissioner after the Commissioner's denial

RR No. 18-2013 expressly states that a motion for reconsideration of the Commissioner's denial does not toll the 30-day period for appeal to the CTA.

Evidence to preserve immediately

Keep a complete chronological assessment file containing the Letter of Authority and related notices, Notice of Discrepancy, PAN, PAN response, FLD/FAN and Details of Discrepancies, proof of receipt and envelopes, protest letter, proof of filing, all supporting documents submitted, transmittal letters, BIR correspondence, FDDA, administrative appeal documents, and proof of receipt of every BIR decision.

Separately preserve the accounting and transactional evidence supporting the merits of the protest. Electronic records should be backed up in their original form where possible.

A tax case can turn as much on proof of dates and service as on tax computation.

When legal help is urgent

Seek tax counsel promptly if the FLD/FAN protest deadline is approaching; you have received an FDDA; a 60-day document deadline or 180-day period is about to expire; the BIR has issued or threatened collection measures such as distraint, levy, or garnishment; the assessment involves substantial amounts or several tax types; there are allegations of fraud or possible criminal exposure; the validity of the Letter of Authority or service of notices is disputed; or a CTA petition may be necessary.

CTA litigation has procedural and jurisdictional requirements that are separate from writing an administrative protest. Waiting until the last few days can unnecessarily narrow available remedies.

Frequently asked questions

Do I need to pay the assessment before filing the administrative protest?

Section 228 allows an FLD/FAN to be administratively protested without first requiring payment of the disputed deficiency as a condition to that protest. If you accept part of the assessment, however, BIR procedures contemplate settlement of the accepted portion while the disputed portion proceeds separately. (BIR)

Does the 30-day period start from the date written on the FLD/FAN?

Generally, the protest period is reckoned from receipt, not merely from the date printed on the assessment. Proof of service and receipt should therefore be preserved.

Can I simply ask for "reconsideration or reinvestigation" in the alternative?

The regulations require the taxpayer to state the nature of the protest. The two remedies are different, particularly because reinvestigation involves additional evidence and carries the 60-day documentary requirement. It is safer to make a deliberate, legally supportable choice rather than leave the remedy ambiguous.

What happens if the BIR does not decide my protest in 180 days?

Depending on the applicable stage, you may generally appeal the inaction to the CTA within the next 30 days or elect to wait for the BIR's final decision and appeal that decision within 30 days of receipt. Those remedies are mutually exclusive once one is chosen. (Lawphil)

Can I appeal an FDDA issued by a Regional Director directly to the CTA?

Yes. RR No. 18-2013 allows a taxpayer whose protest is denied by the Commissioner's duly authorized representative either to appeal to the CTA within 30 days or elevate the matter to the Commissioner through a request for reconsideration within the same period.

Can I submit more evidence when I appeal the FDDA to the Commissioner?

The administrative appeal provided by RR No. 18-2013 is a request for reconsideration, not reinvestigation. The regulation states that no request for reinvestigation is allowed at that stage.

What if I received a warrant of distraint or levy even though I believe my protest is unresolved?

Do not ignore it. Depending on the history of the assessment, a collection notice or warrant can raise questions about whether the BIR has already taken a position amounting to a final denial and whether CTA remedies must be invoked. Supreme Court decisions show that the characterization depends heavily on the particular communications and procedural history. (Lawphil)

Official sources

General-information disclaimer

This article provides general Philippine legal information and is not a substitute for legal or tax advice based on the actual assessment, audit record, service documents, tax type, taxable period, and procedural history of a particular taxpayer. Assessment and CTA deadlines can determine whether a remedy remains available, so the relevant documents and dates should be reviewed individually.

Sources checked and law verified as of August 25, 2026.