Mexico's 2027 Income Tax Reform: When an Arm's Length Margin Is No Longer Enough

Mexico has approved a reform to its Income Tax Law (Ley del Impuesto sobre la Renta, or LISR) as part of the 2027 Economic Package. The bill was submitted by the Federal Executive on September 8, 2026, approved without changes by the Chamber of Deputies, and approved by the Senate on October 27, 2026. The Senate introduced a single targeted amendment to Article 78-E, which expands the list of taxpayers excluded from the new deduction control mechanism to include the terminal automotive industry operating under a bonded-warehouse authorization for vehicle assembly and manufacturing, as well as businesses that sell and distribute gasoline and diesel. That provision has been returned to the Chamber of Deputies for a final vote before the law is published in the Official Gazette (Diario Oficial de la Federación). The rest of the text, including every measure discussed in this article, has already cleared both chambers in identical terms. The reform takes effect on January 1, 2027.

For multinational groups headquartered in the United States, Europe and Asia, the most important message is counterintuitive. The reform leaves Mexico's transfer pricing regime essentially untouched: the documentation requirements, the Master File, Local File and Country-by-Country report, the hierarchy of methods, the comparability rules and the interquartile range all remain as they were. What changes are the general deduction rules that sit underneath the transfer pricing analysis. As a result, a Mexican subsidiary can have a well-designed transfer pricing policy, a result inside the arm's length range and robust documentation, and still end up with a taxable profit, an effective tax rate and a cash tax bill that no longer reflect its economic reality.

This article focuses on the three measures with the most direct impact on related-party transactions: the new timing rule for deducting payments to foreign residents, the reduction of the net interest limitation from 30% to 20%, and the new deduction control mechanism that effectively sets a minimum taxable profit for large taxpayers. Special attention is given to the last of these, because it creates a structural risk for limited-risk distributors, commissionaires and other routine entities remunerated with low or tight margins.

1. Payments abroad: deduction now follows payment and withholding

The first measure changes when payments to foreign residents become deductible and when the obligation to withhold Mexican tax arises. Under the reform, payments to foreign residents are deductible only in the fiscal year in which the consideration is actually paid and the corresponding withholding tax, where applicable, is remitted to the tax authorities. At the same time, accrual (devengo) is added as a trigger for the withholding obligation, alongside the moment the payment becomes due and the moment it is made, whichever occurs first.

The combination of both rules opens a timing gap that did not exist before. The withholding obligation can now arise in the year the expense is accrued, while the deduction is pushed to the year in which the cash actually leaves Mexico. For multinational groups, the transactions most exposed are recurring intercompany charges paid to the foreign parent or to regional hubs: royalties for the use of trademarks, technology or know-how; technical assistance; and intragroup services such as management fees, shared-service charges and regional support functions. These are precisely the transactions that are often settled on deferred, netted or open-ended terms, with year-end invoices and intercompany balances carried into the following year.

Illustrative example.
A Mexican subsidiary accrues an annual royalty of MXN 12 million (approximately USD 645,000) payable to its foreign parent and settles it in the following year. Assuming a 10% treaty withholding rate, the subsidiary could be required to remit MXN 1.2 million (about USD 65,000) of withholding tax during 2027, while the deduction would only be available in 2028. With the corporate income tax rate at 30%, the deferral increases the 2027 tax bill by approximately MXN 3.6 million (about USD 194,000). Combined with the earlier withholding, the 2027 cash outlay would reach roughly MXN 4.8 million (about USD 258,000), even though the royalty itself may be perfectly arm's length.

The same logic applies to year-end transfer pricing adjustments that take the form of an additional service or royalty charge to the foreign parent. When the adjustment is calculated after year-end and invoiced or paid in the following year, its deductibility will now depend on the payment date rather than the accrual date. Groups should therefore review intercompany agreements, invoicing calendars, settlement terms and outstanding payables to foreign related parties before the close of 2026, so that the first year under the new rules does not generate an avoidable mismatch between withholding and deduction.

2. Net interest limitation reduced from 30% to 20%

The second measure reduces the cap on the deduction of net interest from 30% to 20% of adjusted taxable profit, a tax measure that broadly approximates EBITDA. The rest of the mechanism remains unchanged: the existing MXN 20 million (about USD 1.1 million) de minimis threshold for net interest, its determination at group level for Mexican entities, and the ability to carry forward non-deductible interest for the following ten years.

From a transfer pricing perspective, this measure separates two questions that are often treated as one. The first is whether the interest rate on an intercompany loan is consistent with the arm's length principle, which is what the transfer pricing study tests. The second is whether the interest is deductible, which now depends to a much greater extent on the borrower's profitability. An intercompany loan can be priced within the market range and properly documented, and the interest can still be partially non-deductible because of the entity's leverage relative to its earnings. For low-margin entities, whose adjusted taxable profit is structurally small, the 20% cap can be reached with relatively modest levels of debt.

Illustrative example.
A Mexican company has adjusted taxable profit of MXN 100 million (about USD 5.4 million) and net interest subject to the limitation of MXN 28 million (about USD 1.5 million). Under the 30% cap, all of the interest would be deductible. Under the new 20% cap, the limit falls to MXN 20 million, leaving MXN 8 million (about USD 430,000) non-deductible in the year and generating approximately MXN 2.4 million (about USD 129,000) of additional income tax. The example is simplified and assumes the group-level de minimis threshold has already been exhausted.

In practice, the financial analysis of the Mexican entity's debt capacity and the transfer pricing analysis of its intercompany financing can no longer be reviewed in isolation. Interest rate, amount of debt, cash flow, repayment profile and the timing of interest payments abroad, which is also affected by the measure described in the previous section, need to be evaluated together.

3. The deduction control mechanism: a minimum taxable profit for large taxpayers

The third measure, and the one with the deepest implications for multinational groups, is the new Chapter X of Title II of the LISR (Articles 78-A to 78-F). It introduces a mechanism to control authorized deductions and tax losses that applies to Mexican legal entities under the general regime with taxable income above MXN 50 million (about USD 2.7 million) that determine a taxable profit for the year.

3.1 How the mechanism works

The mechanism operates in two tiers, depending on the ratio between authorized deductions and taxable income. When deductions exceed 96.67% of taxable income, the deductible amount is capped at exactly 96.67% of that income. This produces a minimum taxable profit equal to 3.33% of taxable income, which at the 30% corporate rate is equivalent to a minimum income tax of approximately 1% of revenue, regardless of how much the entity actually earned. When deductions are equal to or below 96.67% of taxable income, only 99% of those deductions may be claimed, so even entities with comfortable margins lose one percentage point of their deductions every year.

Deductions that cannot be claimed in a given year may be carried forward, adjusted for inflation, for up to 20 years, but they cannot be treated as a tax loss. In addition, for taxpayers subject to the mechanism, tax losses from prior years may offset no more than 50% of the taxable profit for the year, calculated after applying the deduction limit, although the carryforward period for losses is extended from 10 to 20 years. Provisional (monthly) tax payments for 2027 are also increased through an extraordinary adjustment factor applied to the profit coefficient: 1.0658 for taxpayers whose deductions in the prior year were equal to or below 96.67% of income, and 2.6162 for those whose deductions exceeded that threshold. For low-margin entities, this last factor means that the cash impact of the reform will be felt from the first months of 2027, not only when the annual return is filed in 2028.

Article 78-E excludes certain taxpayers from the mechanism. Among the exclusions relevant to foreign investors, maquiladoras are excluded with respect to their maquila income, but not their domestic sales; companies with fewer than five years since their registration with the tax authorities are also excluded, subject to anti-abuse rules for restructurings and transfers of assets or customers from existing entities. The Senate amendment pending final approval would add the terminal automotive industry operating under a bonded-warehouse authorization and fuel retailers to the list. Distribution, commission and routine service entities are not excluded.

3.2 The core risk: an arm's length result that produces a distorted tax result

Limited-risk distributors are a cornerstone of how foreign multinationals operate in Mexico. The typical model is well known to any Tax Director: the Mexican entity buys finished goods from a related party, resells them to third parties in the domestic market, performs routine sales and marketing functions, bears limited inventory, credit and market risks, and is remunerated with a stable, relatively low operating margin benchmarked against comparable independent distributors. The same logic applies to commissionaires and to service providers remunerated on a cost-plus basis. In many industries, the interquartile range for these entities sits between 1% and 4% of sales.

This is exactly the profile that the deduction control mechanism captures. An entity with an operating margin of 2% has deductions equal to roughly 98% of its revenue, which exceeds the 96.67% threshold. Its taxable profit is therefore set at 3.33% of revenue, not at the 2% that its transfer pricing policy, its benchmarking study and its financial statements all support. The transfer pricing result remains correct. What changes is that the tax base is no longer derived from it.

Illustrative example.
A Mexican limited-risk distributor reports taxable income of MXN 800 million (about USD 43 million) and earns an operating margin of 2.0%, within an interquartile range of 1.4% to 3.1%. Its profit is MXN 16 million (about USD 860,000) and, under the current rules, its income tax would be approximately MXN 4.8 million (about USD 258,000). Under the new mechanism, deductions are capped at 96.67% of income, so the taxable profit rises to approximately MXN 26.6 million (about USD 1.4 million) and the income tax to approximately MXN 8.0 million (about USD 430,000). The additional tax of roughly MXN 3.2 million (about USD 172,000) does not arise from a price or margin outside the arm's length range; it arises from the interaction between the transfer pricing regime and a general limit on deductions. The effective tax rate on the entity's real profit rises from 30% to roughly 50%.

Two features of the mechanism make the impact on routine entities more severe than it first appears. First, the carryforward of disallowed deductions offers limited relief to an entity whose remuneration model keeps its deductions structurally above the threshold every year. Because the same cap applies in each subsequent year, the deferred deductions of a limited-risk distributor are likely to remain trapped and may in practice become a permanent cost. Second, the test is applied to tax deductions against taxable income, not to the operating margin used as the profit level indicator in the transfer pricing study. Items below operating profit, such as interest expense, foreign exchange losses, the annual inflation adjustment and year-end transfer pricing adjustments payable to the parent, all increase deductions and can push an entity above the threshold even when its operating margin appears safe.

For entities remunerated on a cost-plus basis, including commissionaires and intragroup service providers, the equivalent threshold is a markup of approximately 3.45% on total costs. Any markup below that level places deductions above 96.67% of income and triggers the minimum taxable profit.

4. Transfer Pricing Compliance Timeline for Fiscal Year 2026

The reform applies from fiscal year 2027, but the decisions that determine its impact are made now, and fiscal year 2026 must still be closed and reported under the current rules. Mexico's transfer pricing compliance calendar has several interdependent filings, and foreign headquarters often underestimate how early the process needs to start.

4.1 The fourth quarter: preliminary analysis and intercompany adjustments

The most valuable step for fiscal year 2026 is a preliminary transfer pricing analysis during the last quarter of the year. Its purpose is to project the Mexican entity's results against the arm's length range before the books are closed, identify whether a year-end intercompany adjustment is needed, and document and invoice it in a timely manner. Adjustments identified after the close are harder to support, may create inconsistencies with customs values and VAT, and leave less room to manage their tax effects. This year, the same analysis also serves a second purpose: it is the natural starting point for modelling how the Mexican entity's 2027 results will interact with the new deduction control mechanism and the 20% interest cap.

4.2 Filing deadlines

Taxpayers required to file the Statement of Tax Situation (Información sobre la Situación Fiscal, or ISSIF) together with their annual return must complete the ISSIF related-party annexes by March 31, 2027. These taxpayers should also file the related-party information return, Annex 9 of the Multiple Informative Return (Declaración Informativa Múltiple, or DIM), together with the ISSIF. Taxpayers that are not required to file the ISSIF must file Annex 9 of the DIM by May 15, 2027.

Taxpayers that file a tax-audited financial statement report through the SIPRED system must file Annex 9 of the DIM before submitting the SIPRED, and must complete the SIPRED annexes on related-party transactions, which are due on May 15, 2027. Taxpayers required to file the Local File informative return must also file it by May 15, 2027. In practice, the obligation to file the Local File applies mainly to taxpayers whose prior-year income exceeded the indexed threshold set out in Article 32-H of the Federal Tax Code, currently around MXN 1.06 billion (about USD 57 million).

Finally, December 31 is the deadline for the Master File informative return, for taxpayers required to file it as members of a multinational group, and for the Country-by-Country report, which is filed by Mexican-resident ultimate parent entities of multinational groups, or by Mexican entities designated by a foreign group to file it. The filings for fiscal year 2025 are due on December 31, 2026, only two months from now, while those for fiscal year 2026 will be due on December 31, 2027.

Annex 9 of the DIM, the ISSIF and SIPRED related-party annexes, and the Local File draw on the same transfer pricing documentation, which must therefore be completed before the earliest applicable filing date. Penalties for failing to file or filing incomplete returns range from MXN 86,050 to 172,100 (about USD 4,600 to 9,300) for Annex 9 and from MXN 172,480 to 245,570 (about USD 9,300 to 13,200) for the Local File, Master File and Country-by-Country report, in addition to the potential loss of eligibility for government contracts.

Three key ideas

First, Mexico did not change its transfer pricing rules; it changed the deduction rules beneath them. For the first time, a Mexican subsidiary can comply fully with the arm's length principle and still face a taxable profit, an effective tax rate and a cash tax bill disconnected from its economic reality.

Second, limited-risk distributors, commissionaires and routine service providers with margins below roughly 3.33% of sales, or markups below roughly 3.45% of costs, are the most exposed. For them, the reform functions as a minimum tax of around 1% of revenue, and the solution is not simply to move up in the range, because the mechanism is non- linear and any change must remain defensible in both jurisdictions.

Third, the window to act is the fourth quarter of 2026. Closing fiscal year 2026 correctly, with a preliminary analysis, timely year-end adjustments and a complete compliance calendar, is also the first step in modelling and preparing the Mexican operation for 2027.

Flint Consulting supports multinational groups with operations in Mexico in quantifying the impact of the 2027 reform on their Mexican entities, reviewing intercompany agreements, payment terms and financing structures, modelling the interaction between transfer pricing policies and the new deduction control mechanism, and executing the fiscal year 2026 compliance calendar, from the fourth-quarter preliminary analysis to the Local File, Master File and Country-by-Country report.

Francisco Arballo · Transfer Pricing Partner & International Liaison · francisco@flintconsulting.mx · +52 81 1351 8242 · www.flintconsulting.mx

This article is for general information only and does not constitute tax, legal or accounting advice on any specific case. The examples are hypothetical and simplified, and are presented for illustrative purposes only. U.S. dollar amounts are approximate, based on an exchange rate of MXN 18.6 per USD. The analysis reflects the text of the LISR reform as approved by the Chamber of Deputies and the Senate as of October 30, 2026; the Senate amendment to Article 78-E is pending a final vote in the Chamber of Deputies, and the reform remains subject to publication in the Official Gazette and to the administrative rules the tax authority may issue.