NIS report 2026 in Mexico: how to reach the close with your data in order

The NIS report is the sustainability information that companies in Mexico must prepare under the Sustainability Information Standards (Normas de Información de Sostenibilidad) issued by the CINIF (Mexican Council for Financial Reporting and Sustainability Standards). They took effect on 1 January 2025, and the first filing takes place in 2026 using fiscal-year 2025 data. The second exercise, for 2026, is already under way, and it arrives with stricter rules.

The first NIS report, for fiscal year 2025, was for many Mexican companies a debut with no rehearsal: the standards were new and the processes did not exist. NIS B-1 provided reliefs for that first application, among them the option to omit Scope 3 and the sustainable-investment indicator. With no prior year to compare against, the first report required work but could largely be handled internally.

In the second year the bar rises.

What changes in fiscal year 2026

The second report operates under different rules, and the differences are not minor:

• Comparatives: the 2026 figures are presented alongside those of 2025. If the first report had errors, inconsistencies or weak estimates, they will be exposed the moment the numbers sit side by side.
• Scope 3 without the first-year relief: indirect value-chain emissions, the hardest to measure and, in many sectors, the largest part of the real footprint, come fully into the report.
• Sustainable-investment indicator: this also loses the first-year relief.

Before planning the close, work from the text in force: the CINIF has published improvements to the Sustainability Information Standards for 2026, so the specific requirements for each indicator should be confirmed against the current version.

It is worth recalling the scope of NIS A-1 and NIS B-1: the former sets the conceptual framework and the latter requires companies to determine and disclose 30 Basic Sustainability Indicators (IBSO), spread across three areas (environmental, social and governance). The NIS also sit alongside the international standards IFRS S1 and IFRS S2 from the ISSB, with which they are aligned.

External assurance and ISSA 5000

The international assurance standard ISSA 5000 applies to engagements verifying sustainability information reported for periods beginning on or after 15 December 2026, or as at a specific date on or after that day, and early application is permitted. For a company on a calendar year, that points to fiscal year 2027 as the first one falling squarely under the standard.

ISSA 5000 does not in itself require sustainability information to be assured: it sets out how that assurance is to be performed when it is commissioned. The practical consequence is the same either way: the processes and traceability you build during 2026 are what will have to withstand that level of scrutiny. The difference between a well-documented figure and a number pulled from a spreadsheet with no traceability will show.

The first mistake is starting to collect data too late

The NIS report is not done in December, it is done all year round. Every energy invoice, every fleet trip, every purchase from a supplier generates data that will later be needed to calculate the environmental indicators. If it was not collected properly at the time, it does not disappear: it can be recovered, estimated or reconstructed from whatever is available. But doing it after the fact is an enormous job. It means chasing old invoices, asking suppliers for information after they have already closed the quarter, applying estimates where there should have been real measurements, and documenting every methodological decision so that whoever reviews it understands why the data looks the way it does.

And even then, the result is not the same. A data point collected at the time, with a clear source and full traceability, withstands external review. A data point reconstructed at the close from approximations is one that has to be defended.

Fiscal year 2026 is well under way and much of its data has already been generated. The question is whether someone is collecting it correctly, or whether the close will mean reconstructing it.

The most common mistakes being made right now

The problems that appear in the NIS report's environmental indicators are usually not errors of regulatory interpretation or complex calculation, but process errors:

• Data collected from different sources each year with no fixed criteria.
• Scopes delimited differently depending on who does the calculation.
• Outdated emission factors applied to real consumption.
• Supplier information arriving incomplete, late or in incompatible formats.

These are the same four patterns that repeat in company after company, and most do not detect them until they try to present the comparatives or answer an external reviewer. Knowing them in advance changes the picture: almost all of them have a solution if identified while the year is still open. Once the year closes, the options narrow to justifying the errors or redoing the whole process.

There is still time to get it right

While the year is still open, most companies still have time to review how they collect environmental data, identify the highest-risk indicators and set up the processes they will need when a reviewer arrives. It is not a question of resources or advanced technology: it is knowing exactly where the most common mistakes are and what to do before the close.

To that end, we have prepared a guide with solutions to the most common mistakes in the environmental indicators of the NIS report, everything you need to reach the close of 2026 with your data in order.

Download the guide to common NIS reporting mistakes (in Spanish).

Fiscal year 2026 is still open, but the room to get it right narrows with every month that passes.