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 leap into the void with a safety net. The standards were new and the processes did not exist. The CINIF knew this, which is why NIS B-1 came with two built-in reliefs: both Scope 3 and the sustainable-investment indicator could be omitted in that first year. With no historical comparatives to defend and no external auditor questioning every figure, the first report required work but could be handled internally without too much trouble.

In 2026, everything changes.

What changes in fiscal year 2026

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

• Mandatory comparatives: the 2026 figures must be 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 with no exemption: indirect value-chain emissions, the hardest to measure and, in many sectors, the largest part of the real footprint, become mandatory to report. There is no extension.
• Sustainable-investment indicator: this can no longer be omitted either.

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.

What happens in 2027?

The international assurance standard ISSA 5000 applies to engagements verifying sustainability information for periods beginning on or after 15 December 2026. In practice, this means the 2026 exercise will be among the first to reach an external auditor with instructions to review sustainability information with a rigour similar to that applied to the financial accounts. The difference between a well-documented figure and a number pulled from a spreadsheet with no traceability will start to 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 in January will 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 the auditor 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 an audit. A data point reconstructed in December from approximations is one that has to be defended.

The 2026 exercise has been running for six months. The data from January to June has already been generated. The question is whether someone is collecting it correctly, or whether December 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 auditor. Knowing them in advance changes the picture: almost all of them have a solution if identified while the exercise 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

The second half of 2026 has just begun. For most companies, that means they still have time to review how they collect environmental data, identify the highest-risk indicators and set up the processes they will need when the auditor 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 here

The 2026 exercise is already under way, but there is still time to do it well.