Tax Assessments at Record Highs: Taxpayers Owe 3.1 Trillion Pesos to Mexico’s Tax Authority, and Nearly Two-Thirds Are Under Litigation

The volume of disputed liabilities limits immediate collection and makes the resolution of lawsuits more consequential for public finances.

Tax assessments determined by the Tax Administration Service (SAT) reached 3.1 trillion pesos as of the end of March, an elevated level for a first quarter in the Finance Ministry’s (SHCP) records. What stands out is not only the size of the amount, but its legal status: around 2 trillion pesos—equivalent to 63% of the total—is being challenged through some form of legal appeal filed by taxpayers.

From a public-finance perspective, the disputed figure underscores the scale of the challenge: it exceeds the fiscal deficit projected for the year, estimated at 1.5 trillion pesos, and on its own is comparable to several large-scale social programs. However, these are not resources immediately available to the treasury, but amounts whose recovery depends on audit and collection processes and, in a growing share of cases, litigation that can stretch on for years.

Tax assessments are liabilities the authority determines through its verification powers—audits, desk reviews, electronic reviews, audit opinions, and cross-checks of accounting records and digital information—mainly tied to taxes such as income tax (ISR) and value-added tax (IVA). If they are not paid, surcharges, inflation adjustments, and interest accrue, increasing the final amount. When taxpayers disagree with the assessment, they typically challenge it in court, opening a legal process that, according to specialists, can take between 18 months and three years, and even longer depending on the complexity of the case.

The rise in these amounts is occurring in an environment where revenue collection has taken on greater weight as the anchor of fiscal policy. With public spending pressured by social programs, infrastructure projects, and the financial cost of debt, the government has prioritized increasing revenue without raising broad-based tax rates, relying instead on enforcement, collection efficiency, and digitalization. Under that logic, the growth in tax assessments can be read as a sign of a more active tax authority—though converting them into actual revenue is more uncertain when most end up in dispute.

By the end of the first quarter, roughly 1.8 million tax assessments were recorded, a high volume compared with previous years. At the same time, the number of disputed assessments increased from 195,419 to 200,441 between January and April, marking the highest figure for that period since 2018. It’s not just that there are more disputes—they’re also larger: the average amount per challenged liability rose from 9.8 million to 10 million pesos, well above the levels seen at the end of the last decade.

More Enforcement and More Legal Challenges: The Legal “Bottleneck”

The growth in the contested amount reflects a twofold shift. On the one hand, SAT has expanded its ability to detect inconsistencies using digital tools, database cross-checks, electronic invoicing, and transaction traceability, which reduces room for evasion and increases the likelihood of targeted audits, especially for mid-sized and large taxpayers. On the other hand, companies and individuals with complex operations have also sharpened their defense strategies, turning to legal remedies to challenge the authority’s standards, assessment methodologies, interpretations of anti-abuse rules, and the evidentiary strength of audits.

In this context, the tax justice system becomes an economic factor in its own right: the more cases move into litigation—and the longer they take—the slower the flow of potential revenue to the government. In addition, the buildup of disputed assessments tends to inflate the total outstanding balance, but does not necessarily improve public-sector liquidity. For companies, by contrast, litigation can function as a mechanism for managing financial risk: they aim to win on the merits or, at minimum, manage timelines and contingencies—factors that can influence investment decisions, accounting provisions, and access to financing.

SHCP statistics show that SAT maintains a high final-instance win rate, close to 79%. Even so, the share of cases lost increased from 17.5% in the first quarter of 2025 to 19.6% in the first quarter of 2026. In practical terms, even a moderate change in the loss rate can matter when the average amounts at stake are rising and the universe of cases is expanding.

For fiscal policy, the challenge is to balance the intensity of enforcement with the technical quality of the authority’s actions: better-supported audits tend to reduce the probability of losing cases and increase effective revenue collection. For taxpayers, the challenge is complying within an increasingly demanding, documentation-heavy regulatory framework, where differences in interpretation, deductions, credits, or the substantive economic reality of transactions can trigger costly reviews.

Looking ahead, the size of the litigated balance suggests that revenue collection will continue to depend to a significant extent on the state’s ability to resolve disputes quickly and with strong legal grounding. If the legal backlog grows, the result could be slower collection and greater uncertainty around revenues—just as the budget faces pressures from the economic cycle, public investment needs, and the broader stability of public finances.

In short, the record level of tax assessments and the increase in disputed liabilities confirm a more active SAT and a more frequently used tax defense toolkit; the net outcome will depend on the quality of audits and the legal system’s capacity to turn assessments into actual revenue.