Quick answer

If you received a Formal Letter of Demand and Final Assessment Notice (FLD/FAN), you generally have 30 days from receipt to file a valid written administrative protest with the BIR official who issued or signed it. Choose either:

Request for reconsideration — asks the BIR to re-evaluate the assessment using records already submitted; or
Request for reinvestigation — relies on newly discovered or additional evidence.

The protest must address every disputed item separately, state the material facts and applicable legal grounds, identify the assessment date, and specify the type of protest. For a reinvestigation, all relevant supporting documents must be submitted within 60 days from filing the protest.

Missing the 30-day protest deadline can make the assessment final, executory, and demandable. A general request for more time, an informal meeting, or an unsupported letter saying “we disagree” may not be a valid protest.

First identify the document you received

Different BIR notices trigger different responses:

Document	What it means	General response period
Notice of Discrepancy	Initial audit findings; not yet a final assessment	Participate promptly in the scheduled Discussion of Discrepancy and submit the requested explanation and evidence within the period stated in the notice
Preliminary Assessment Notice (PAN)	Proposed deficiency assessment	15 days from receipt to respond
FLD/FAN	Formal assessment and demand for payment	30 days from receipt to file an administrative protest
Final Decision on Disputed Assessment (FDDA)	BIR decision on the protest	Generally 30 days from receipt to appeal to the Court of Tax Appeals
Collection letter, warrant of distraint or levy, or garnishment notice	Collection has begun or is imminent	Obtain legal help immediately; the document may affect the CTA appeal period

A PAN is generally required before an FLD/FAN, but Section 228 of the Tax Code allows an outright FLD/FAN in specified cases, including certain mathematical errors, withholding discrepancies, improper carryover of an amount also claimed as a refund or tax credit, unpaid excise tax, and transfers of exempt articles to non-exempt persons.

Do not ignore a PAN merely because the formal protest comes later. A timely, complete PAN response may resolve factual errors and preserves a clear record of your objections.

Step 1: Record the date and manner of receipt

The protest period runs from receipt, not simply from the date printed on the assessment. Immediately preserve:

The original notice and all attached assessment schedules;
The envelope, registry notice, courier pouch, tracking record, and proof-of-delivery details;
The name and position of the person who received it;
The date, time, and place of delivery;
Any email or electronic notification connected with the notice; and
Your BIR registration records showing the registered address at the relevant time.

BIR notices may be served personally, through substituted service, or by mail or courier under the applicable regulations. Service on an appointed tax agent may be treated as service on the taxpayer. Delivery to a clerk or person in charge at a registered or known business address can also be legally significant.

Count every deadline conservatively. Do not assume that an informal discussion, request for records, settlement proposal, or request for extension suspends the statutory period.

Step 2: Check the assessment for procedural and substantive defects

Review the entire audit history, not only the amount demanded. Relevant questions include:

Was the examination covered by a valid Letter of Authority or electronic Letter of Authority?
Were the revenue officers who conducted the examination properly authorized?
If an officer was replaced, was an appropriate replacement authority issued?
Did the examination remain within the taxpayer, taxable period, tax types, transactions, and scope authorized?
Were the required notices properly served?
Was a PAN issued, unless a statutory exception applied?
Were you allowed the full response period before the FLD/FAN was issued?
Did the PAN and FLD/FAN explain the material facts and legal bases instead of merely listing amounts?
Does the FLD/FAN clearly fix the liability and make a definite demand for payment?
Was the assessment issued within the applicable prescriptive period?
Were returns, payments, withholding credits, prior assessments, and previously settled amounts properly recognized?
Are the tax base, rate, surcharge, interest, and arithmetic correct?

Under the 2026 audit framework, replacement electronic Letters of Authority may validly continue an existing audit when the taxpayer, period, and authorized scope remain unchanged. Whether a particular authority or replacement is valid depends on the documents and actual conduct of the examination.

Procedural defects should be raised expressly in the protest. Do not assume the CTA will consider an unpleaded factual issue later. The Supreme Court has cautioned against deciding Letter of Authority defects that were never properly put in issue and supported by evidence.

Even if you believe the assessment is void, file a timely protective protest and, when necessary, a timely CTA appeal. Simply ignoring the notice is dangerous.

Step 3: Choose the correct type of protest

Request for reconsideration

Choose reconsideration when the existing BIR docket already contains the evidence needed to decide the case. It asks for re-evaluation without additional evidence and may involve factual or legal questions.

The special 60-day document-submission period under Revenue Regulations No. 18-2013 does not apply to reconsideration. That does not make an incomplete protest safe: identify and attach the existing records on which you rely whenever practicable.

Request for reinvestigation

Choose reinvestigation when you need the BIR to consider newly discovered or additional evidence. The protest must specify the evidence you intend to present.

All relevant supporting documents must be submitted within 60 days from filing the protest. Missing that deadline can bar the taxpayer from contesting the assessment through additional evidence and lead to denial of the protest.

Do not label a protest “reconsideration and/or reinvestigation” without deciding which procedure you are invoking. The choice affects documentary deadlines and the starting point of the BIR’s 180-day action period.

Step 4: Prepare an issue-by-issue protest

A valid protest should contain, at minimum:

The taxpayer’s registered name, TIN, address, and contact information;
The assessment number, tax type, taxable period, assessment date, amount, and date of receipt;
An express statement that the letter is a request for reconsideration or reinvestigation;
For reinvestigation, a description of the newly discovered or additional evidence to be submitted;
A separate discussion of every assessment item being disputed;
The material facts supporting the taxpayer’s position on each item;
The applicable Tax Code provisions, regulations, and controlling jurisprudence;
A reconciliation or corrected computation, where applicable;
A list of attachments and the purpose of each document;
The precise relief requested, such as cancellation or reduction of specified assessment items; and
The taxpayer’s or authorized representative’s signature and appropriate proof of authority.

A practical issue format is:

Assessment item: State the disputed adjustment and amount. BIR position: Summarize the factual and legal basis shown in the FLD/FAN. Taxpayer’s facts: Explain what occurred, with dates and document references. Legal basis: Cite the applicable law, regulation, or decision. Reconciliation: Show the correct tax treatment and computation. Requested action: Ask that the item be cancelled or reduced to a stated amount.

Address every item you intend to dispute. Under Revenue Regulations No. 18-2013, an item not protested—or not supported by facts and legal grounds—may be treated as undisputed and become final, executory, and demandable.

A catch-all statement reserving the right to raise additional objections is not a substitute for a valid, issue-specific protest.

Step 5: File it with the correct BIR office

The protest to the FLD/FAN should be filed with the duly authorized BIR representative who signed or issued the assessment, following the instructions on the notice. An administrative appeal from that representative’s adverse decision is filed with the Office of the Commissioner.

Before filing, confirm the receiving office and its currently accepted submission arrangements. Do not rely solely on an ordinary email, an informal handoff to the examining revenue officer, or an unverified electronic channel.

Obtain strong proof of filing, such as:

A complete copy bearing the official BIR receiving stamp, date, and receiving officer’s details;
An official acknowledgment for every volume or attachment submitted;
A detailed document inventory signed or stamped by the receiving office; and
Any official mailing or transmission record allowed by the receiving office.

If filing through a representative, attach the authorization appropriate to the taxpayer and transaction. Keep an identical, paginated copy of everything filed.

Step 6: Submit and preserve the evidence

Depending on the assessment, relevant evidence may include:

Filed tax returns, amended returns, and confirmation receipts;
Proof of tax payment and bank validation;
Certificates of creditable tax withheld, including BIR Forms 2307;
Audited financial statements and trial balances;
General ledgers, subsidiary ledgers, journals, and reconciliations;
Sales invoices, purchase invoices, and supporting accounting documents;
Contracts, purchase orders, delivery records, and acceptance documents;
Bank statements and proof of remittance;
Payroll records and withholding schedules;
Importation, excise-tax, or registration documents;
Tax treaty documents and tax-residency certificates, where applicable;
The original and replacement LOA or eLA;
The Notice of Discrepancy, PAN, FLD/FAN, and all details of discrepancies;
Written submissions, meeting minutes, and BIR acknowledgments;
Valid waivers of the statute of limitations, if any; and
Proof concerning service or non-service of assessment notices.

Explain what each document proves. A box of unorganized records is less useful than an indexed submission tied to each disputed item.

Preserve original documents. Where the BIR accepts certified reproductions, keep the originals ready for verification. Foreign-issued documents may require authentication or an apostille, depending on the document and intended use.

Step 7: Track the BIR’s 180-day period

The starting point depends on the type of protest:

For a request for reconsideration, the 180-day period is generally counted from filing the protest.
For a request for reinvestigation, it is generally counted from submission of the required supporting documents within the 60-day period.
For an administrative appeal to the Commissioner, Revenue Regulations No. 18-2013 also provides a 180-day action period counted from filing the administrative appeal.

If the protest is denied by a duly authorized BIR representative, you generally have two alternatives within 30 days from receipt:

Appeal directly to the CTA; or
Elevate the matter to the Commissioner through a request for reconsideration.

No reinvestigation is allowed at that administrative-appeal stage, and only issues addressed in the authorized representative’s decision will be entertained by the Commissioner.

If the Commissioner denies the protest or administrative appeal, the taxpayer generally has 30 days from receipt to appeal to the CTA. Filing another motion for reconsideration with the Commissioner does not suspend that 30-day CTA period.

What if the BIR does not act within 180 days?

The taxpayer generally has two mutually exclusive choices:

File a petition for review with the CTA within 30 days after the 180-day period expires; or
Wait for the BIR’s final decision and appeal within 30 days after receiving it.

The Supreme Court confirmed this choice in Lascona Land Co., Inc. v. Commissioner of Internal Revenue. Once the taxpayer chooses the inaction appeal and files in the CTA, the taxpayer cannot also pursue the wait-for-a-decision route.

Calculate the 180-day period and the following 30-day window with counsel. An appeal filed too early, too late, or from the wrong document may be dismissed.

Appealing to the Court of Tax Appeals

A CTA appeal is commenced by filing a petition for review with the CTA in Division. The petition is a formal court pleading, not another letter to the BIR. It must comply with the CTA Law, Revised Rules of the CTA, applicable Rules of Court, docket-fee requirements, service rules, verification requirements, and current paper and electronic-submission procedures.

CTA filing rules have changed in recent years, particularly for electronic copies and initiatory pleadings. Do not assume that emailing a petition by the deadline validly commences the case. Check the CTA’s current filing guidance and have counsel confirm the permitted filing mode before the deadline.

An appeal to the CTA does not automatically stop tax collection. Under Section 11 of Republic Act No. 1125, as amended, the CTA may suspend collection when collection may jeopardize the interests of the government or taxpayer. The court may require a deposit or a surety bond of up to twice the amount claimed. A request for suspension must be supported by evidence; it should not be treated as automatic relief.

Common mistakes that can lose the protest

Treating a PAN response as the protest to the later FLD/FAN;
Filing more than 30 days after receipt of the FLD/FAN;
Sending the protest only to the examining revenue officer instead of the issuing authorized official;
Failing to identify whether the protest is for reconsideration or reinvestigation;
Omitting facts or legal grounds for one or more assessment items;
Disputing only the total amount without addressing each adjustment;
Requesting reinvestigation but missing the 60-day documentary deadline;
Relying on an informal promise that the deadline will be extended;
Failing to preserve proof of receipt and proof of filing;
Assuming negotiations, compromise proposals, or voluntary payments suspend appeal periods;
Filing another BIR motion after a Commissioner-level denial and allowing the CTA period to expire;
Appealing to the CTA before the proper decision or inaction period exists;
Treating a collection letter or warrant as routine correspondence; or
Raising an LOA, service, prescription, or due-process issue only after the case reaches court.

When legal help is urgent

Consult a Philippine tax lawyer immediately if:

The 30-day protest or CTA deadline is approaching;
The assessment has multiple tax types or taxable periods;
The BIR alleges fraud, deliberate falsity, tax evasion, or failure to file returns;
You received a subpoena, criminal complaint, or notice of referral to prosecutors;
A warrant of distraint or levy, garnishment notice, or notice of sale has been issued;
The BIR has contacted customers, banks, tenants, or debtors about your liability;
The assessment is based on third-party data you cannot reconcile;
The audit was conducted by officers not named in the LOA or eLA;
Notices were sent to an old or incorrect address;
A waiver of the statute of limitations is disputed;
The BIR issued the FLD/FAN before your PAN response period expired;
The FDDA does not clearly state its factual and legal bases; or
The protest period may already have expired.

A late protest normally cannot revive a final assessment. Questions about defective service, a void assessment, prescription, or an improper collection measure may still require analysis, but they should not be treated as substitutes for timely filing.

Frequently asked questions

Must I pay the assessment before filing a BIR protest?

Section 228 does not generally require full payment as a condition for filing the administrative protest. However, amounts attributable to issues you do not validly dispute may become final and collectible. A later CTA appeal also does not automatically suspend collection.

Can I protest only the penalties or interest?

Yes, but identify the particular penalties or interest computations being challenged and state the factual and legal basis. Any unchallenged basic tax or other assessment item may become final.

Can I ask the BIR for an extension of the 30-day protest period?

Do not rely on an extension. The 30-day period is statutory, and an informal request or accommodation does not safely preserve the protest.

Is a letter saying “we disagree and request reconsideration” enough?

Not necessarily. The protest must identify its nature, the assessment, and the factual and legal basis for each disputed issue. Unsupported or incomplete objections may be treated as void or may leave particular items undisputed.

Does the 60-day document period apply to every protest?

Under Revenue Regulations No. 18-2013, it applies to a request for reinvestigation, not to a request for reconsideration. A reconsideration should nevertheless identify the existing records supporting the taxpayer’s position.

Can I go directly to the CTA after receiving the FLD/FAN?

Ordinarily, no. The taxpayer must first file a timely administrative protest. Directly appealing the assessment without exhausting the required administrative remedy can result in dismissal.

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

Substance can matter more than the label. A letter or collection action that clearly and finally rejects the taxpayer’s position may, in some circumstances, be treated as a final or constructive denial. Because that can start a 30-day CTA period, obtain advice immediately.

Does a defective FDDA automatically cancel the original assessment?

Not necessarily. The Supreme Court explained in Commissioner of Internal Revenue v. Liquigaz Philippines Corporation that invalidity of the FDDA does not automatically invalidate an otherwise valid assessment. The correct procedural response depends on the documents and circumstances.

How long does the BIR generally have to assess?

The ordinary assessment period is generally three years under Section 203 of the Tax Code. A ten-year period may apply in cases involving failure to file or a false or fraudulent return with intent to evade tax. Valid waivers and statutory suspensions can affect the calculation. Prescription is highly document- and date-specific.

Official legal sources

This article provides general Philippine legal information, not legal or tax advice for a particular assessment. Deadlines and remedies depend on the actual notices, proof of receipt, audit records, and procedural history. Sources and procedures were checked as of 3 August 2026.