The 30% Rule: When Underdeclared Sales Trigger the 50% Fraud Surcharge

Under Section 248(B) of the National Internal Revenue Code (NIRC), failing to report sales, receipts, or income in an amount exceeding 30% of what a return declares — or overstating deductions by more than 30% of the actual amount — is prima facie evidence of a false or fraudulent return. That finding does not convict anyone of fraud by itself, but it shifts the burden to the taxpayer and opens the door to the steeper 50% surcharge instead of the ordinary 25% rate that applies to a simple late or incorrect filing.

This guide walks through the statutory text, how the 30% figure is actually computed, what “rebuttable” means in practice, and a worked example comparing the two surcharge outcomes. For the broader penalty framework this rule sits inside, see BIR late filing penalties: Section 248 surcharge, Section 249 interest, and RMO 7-2015 compromise; for how this civil presumption relates to criminal exposure, see civil vs criminal BIR tax liability.

What does Section 248(B) actually say? #

Section 248(B) is the provision of the NIRC that raises the ordinary 25% late-filing surcharge to 50% for willful neglect to file or a willfully false or fraudulent return, and it defines exactly when an underdeclaration is “substantial” enough to presume fraud. The 30% figure is not a BIR policy or a Revenue Regulation gloss — it is written into the Code itself as the line between an honest discrepancy and a presumptively fraudulent one.

The operative text reads:

“(B) In case of willful neglect to file the return within the period prescribed by this Code or by rules and regulations, or in case a false or fraudulent return is willfully made, the penalty to be imposed shall be fifty percent (50%) of the tax or of the deficiency tax, in case any payment has been made on the basis of such return before the discovery of the falsity or fraud: Provided, That a substantial underdeclaration of taxable sales, receipts or income, or a substantial overstatement of deductions, as determined by the Commissioner pursuant to the rules and regulations to be promulgated by the Secretary of Finance, shall constitute prima facie evidence of a false or fraudulent return: Provided, further, That failure to report sales, receipts or income in an amount exceeding thirty percent (30%) of that declared per return, and a claim of deduction in an amount exceeding thirty percent (30%) of actual deductions, shall render the taxpayer liable for substantial underdeclaration.”

Two things are doing separate work in this text: the first proviso says a “substantial” gap is prima facie evidence of fraud; the second proviso pins “substantial” to a specific number — more than 30%. Without that second proviso, “substantial” would be left to case-by-case argument. With it, the test is arithmetic.

How does the 25% surcharge differ from the 50% fraud surcharge? #

Section 248 sets two different surcharge rates depending on what the taxpayer did wrong: 25% under Section 248(A) for late filing, filing in the wrong venue, failure to pay tax shown on a return, or failure to pay an assessed deficiency on time, versus 50% under Section 248(B) for willful neglect to file or a willfully false or fraudulent return. The 30% underdeclaration test is what typically supplies the evidentiary basis for the BIR to treat a return as falling into the second, harsher category.

This is a distinct question from the general surcharge-and-interest mechanics covered in the BIR late filing penalties guide — that guide covers Sections 248 and 249 broadly and the RMO No. 7-2015 compromise; this post isolates the specific 30% arithmetic test that pushes a case from the 25% row into the 50% row.

How is the 30% underdeclaration percentage computed? #

The 30% test compares the amount of unreported sales, receipts, or income against the amount already declared on the return — not against the taxpayer’s true total revenue. That distinction matters because it means the percentage can look larger than an intuitive “share of total sales” calculation would suggest, since the denominator is the smaller, already-declared figure.

Worked example: a retail business files its annual return declaring ₱2,000,000 in gross sales. During an audit, the BIR’s third-party matching (e.g., against supplier or buyer records) determines actual gross sales for the year were ₱3,000,000.

1. Unreported sales: ₱3,000,000 − ₱2,000,000 = ₱1,000,000
2. Percentage of declared sales unreported: ₱1,000,000 ÷ ₱2,000,000 = 50%
3. Compare to the 30% threshold: 50% exceeds 30%, so the underdeclaration is “substantial” under Section 248(B), giving rise to prima facie evidence of a false or fraudulent return.

Assume the deficiency income tax computed on the ₱1,000,000 in unreported sales (after allowable costs) comes to a straightforward ₱250,000 deficiency tax for illustration. The surcharge outcome then differs sharply depending on which subsection applies:

The 50% treatment doubles the surcharge on the same deficiency amount — before Section 249 deficiency interest is even added, and before considering that a false or fraudulent return can extend the BIR’s assessment period to ten years from discovery under Section 222(a), instead of the ordinary three-year period.

Is the 30% presumption automatic, or can a taxpayer rebut it? #

Section 248(B) creates prima facie evidence, not conclusive proof — the presumption is rebuttable, meaning a taxpayer who crosses the 30% threshold is not automatically found to have committed fraud. “Prima facie” means the BIR does not need to independently prove fraudulent intent before assessing the 50% surcharge; instead, once the arithmetic threshold is met, the burden shifts to the taxpayer to come forward with an explanation.

A taxpayer can typically rebut the presumption by showing the shortfall arose from something other than intentional concealment, for example:

• A genuine timing difference — income properly recognized in a different period under accrual rules, later matched against a supplier’s reporting for a different year.
• An inadvertent bookkeeping or reconciliation error, documented and corrected, without a pattern of concealment.
• A defensible legal position on how a specific receipt or deduction should be characterized, taken in good faith and disclosed rather than hidden.
• Evidence that the BIR’s third-party data itself is inaccurate or double-counted (a common issue when sales are matched against multiple external sources).

According to a Grant Thornton Philippines commentary on the prescriptive period for false returns, a substantial underdeclaration “does not automatically equal a criminal conviction for tax evasion,” and the presumption “may constitute prima facie evidence relevant to a false or fraudulent return but does not automatically establish criminal guilt” (Grant Thornton, “Prescriptive period on false return”). That distinction — presumption versus proof — is the core of why this rule is described as rebuttable rather than automatic.

In Commissioner of Internal Revenue v. Asalus Corporation, G.R. No. 221590, decided by the Supreme Court on February 22, 2017, the Court applied the Section 248(B) 30% underdeclaration standard to a VAT assessment dispute. The Court held that Asalus’s underdeclaration of taxable sales, receipts, or income exceeded the 30% threshold, which made the return prima facie false; because the return was found prima facie false, the BIR was entitled to rely on the ten-year prescriptive period for assessment under Section 222(a) of the NIRC rather than the ordinary three-year period, and the Court explained that once substantial underdeclaration is shown, the taxpayer bears the burden of overcoming the presumption rather than the BIR bearing the initial burden of proving fraud outright (Supreme Court E-Library, G.R. No. 221590 decision). Note that Asalus turned on the prescriptive-period consequence of a prima facie false return, not directly on imposing the 50% surcharge — but the same 30% mechanism and the same “prima facie, not conclusive” framing apply to both consequences under Section 248(B).

Why this matters for how a business reports sales and receipts #

The 30% rule is ultimately about the quality of the sales and receipts figures a taxpayer reports, since the BIR’s third-party matching programs (from suppliers, buyers, payment processors, and other government data) routinely surface gaps between a filed return and external records. A business that reconciles its own books against every issued BIR Form 2307 it receives, every sales invoice, and its own accounting records before filing reduces the risk of an accidental gap large enough to cross 30% in the first place.

This is a reporting-accuracy issue, not primarily a legal-defense issue — most substantial underdeclarations that end up litigated started as a data or process gap rather than a deliberate concealment. Consistent, complete withholding and sales documentation is the practical first line of defense against ever triggering the presumption.

Summary #

The 30% rule under Section 248(B) of the NIRC is a specific, numeric test: underdeclaring sales, receipts, or income by more than 30% of what a return reports (or overstating deductions by the same margin) is prima facie evidence of a false or fraudulent return, opening the door to the 50% fraud surcharge in place of the ordinary 25% rate under Section 248(A) — and potentially the ten-year assessment period under Section 222(a), as illustrated in CIR v. Asalus Corporation. The presumption is rebuttable: a taxpayer who can show the gap came from honest error rather than intentional concealment is not automatically guilty of fraud, but the burden of proof shifts to them once the threshold is crossed. Accurate, well-documented sales and receipts reporting is the most direct way to avoid the question ever coming up.

Frequently asked questions #

What is the 30% rule under NIRC Section 248(B)? #

The 30% rule is the statutory threshold in Section 248(B) of the National Internal Revenue Code (NIRC) under which failing to report sales, receipts, or income in an amount exceeding 30% of what a return declares — or claiming deductions exceeding 30% of actual deductions — constitutes prima facie evidence of a false or fraudulent return.

Does exceeding the 30% threshold automatically mean a taxpayer committed fraud? #

No. Section 248(B) creates only a rebuttable presumption. Prima facie evidence shifts the burden to the taxpayer to explain the discrepancy, but a taxpayer who shows the shortfall came from an honest error, a timing difference, or a defensible interpretation of the rules — rather than intentional concealment — can overcome the presumption.

What surcharge applies once the 30% threshold is crossed? #

Section 248(B) imposes a 50% surcharge on the tax or deficiency tax once willful neglect to file, or a willfully false or fraudulent return, is established — as opposed to the ordinary 25% surcharge under Section 248(A) for late filing, late payment, or an unpaid deficiency. The 30% underdeclaration test is the mechanism that creates the presumption pointing toward the 50% treatment; the BIR must still tie the underdeclaration to a false or fraudulent return before the 50% rate applies.

How is the 30% underdeclaration percentage calculated? #

The percentage is calculated by comparing the amount of sales, receipts, or income that was not reported against the amount actually declared on the return, not against the true total. For example, if a taxpayer declared ₱2,000,000 in sales but the BIR determines actual sales were ₱3,000,000, the ₱1,000,000 shortfall is 50% of the ₱2,000,000 declared — well past the 30% threshold.

Is there a court decision applying the 30% underdeclaration rule? #

Yes. In Commissioner of Internal Revenue v. Asalus Corporation, G.R. No. 221590 (February 22, 2017), the Supreme Court applied Section 248(B)’s 30% underdeclaration standard to find that the taxpayer’s return was prima facie false, which in that case supported the BIR’s use of the ten-year prescriptive period for assessing tax on a false or fraudulent return.