For years, an invoice and a proof of payment were enough to deduct an expense. That’s over. Today, building a materiality file is the only real way to protect your deductions and your creditable VAT before the SAT. In this guideline we explain what it is, what it must contain, and how to organize it so it survives a review.
What is materiality?
Materiality is the concrete, verifiable evidence that an operation actually happened: that the goods were delivered or the service was genuinely rendered. It isn’t a procedure or a form; it’s the economic substance behind each CFDI.
The concept isn’t expressly defined in the law, but PREDECON (the taxpayer ombudsman), the counts and the Supreme Court have consolidated it as the axis of modern tax enforcement. In practice, it requires proving three things: that the operation existed, that it had a business reason, and that it’s consistent with your activity.
Why the CFDI is no longer enough
The 2026 tax reform was clear: Article 29-A of the Federal Tax Code now requires every CFDI to cover existing, true operations and real legal acts. And the new Article 29-A Bis lets the authority verify the truthfulness of a receipt within its existing powers., without a separate proceeding.
The fundamental shift is the burden of proof: it’s not the authority that must show the operation didn’t exist – it’s you who must prove that it did. And you have to do it with evidence that is suitable, sufficient and contemporaneous with the fact.
- The CFDI proves the form, not the substance of the operations.
- Accounting records and transfers, on their own, don’t establish materiality.
- Without a file, a valid operation can be presumed nonexistent under Article 69-B.
The evidentiary trilogy
To rebut a presumption of nonexistence, the file rests of three pillars. if one is missing, the defense weakens.
Documentary support
Contract with a certain date (fecha cierta), purchase or service orders, quotes, and the communication that negotiated the operations: emails, minutes, corporate messages. It’s the backbone of the file.
Evidence of the deliverable
The proof that the work was carried out: delivery-acceptance records, technical reports, logs, photographs, attendance lists, transport waybills. What demonstrates the real result.
Economic substance
The coherence between the expense, your line of business and your benefit: that the operation has a business reason and that the supplier had the capacity to fulfill it.
The materiality file
This is the minimum content we recommend assembling for each significant operation. Organize it by supplier of by CFDI.
| Block | Key documents |
| From the supplier | Current tax status certificate, compliance opinion (32-D), and verification that it isn’t on the 69-B list. |
| Contractual | Signed contract with a certain date, purchase or service order, quote and technical proposal. |
| CFDI and payment | CFDI compliant with Articles 29 and 29-A, accounting entry with attached evidence, and bank statement proving the flow. |
| Execution | Deliverables, delivery records, reports, logs, photographs and emails that narrate the operation. |
Certain date and NOM-151
A silent risk: the authority can reject editable PDFs, emails, or photos, arguing they could have been created later to simulate compliance. That’s why digital evidence needs traceability.
Certification under NOM-151 gives you digital files solid evidentiary weight by fixing the date and integrity of the document. It’s best to certify key contracts and deliverables at the moment – not once the request has already arrived. A relevant point: a thesis published in October 2025 set requirements for photographs to be admitted as proof of materiality; improvised evidence no longer convinces.
How to organize the file
The difference between a company that survives a review and on that faces multimillion-peso assessments is usually order. A simple method:
- Create a digital folder per supplier and, inside, a subfolder per CFDI of high-value operation.
- Gather the evidence at the time of the operation, not at year-end close.
- Verify the supplier before paying: tax status, compliance and the 69-B list.
- Certify sensitive documents with NOM-151 to give them a certain date.
- Periodically review the largest of most unusual operations, which are the first to be audited.
Mistakes that cost dearly
- Building the file only when the SAT’s request arrives.
- Relying on good faith: hiring a supplier without verifying its capacity.
- Keeping screenshots or printouts with no certification or tracebility.
- Having a contract but not proving delivery, or having deliverables with no contract.
- Mixing the materiality of many operations in a single folder with no order.
Frequently asked questions
Is the CFDI alone enough?
No. The CFDI is necessary, but on its own it doesn’t prove the operation happened. You need the complete file.
How long should I keep it?
Accounting and its supporting documentation must be kept in accordance with Article 30 of the CFF; as a practical rule, at least five years, and longer for operations with prolonged effects.
Are photos valid?
They can be, if they meet the requirement the authority set: that they identify place, date and operation, and that they’re backed by the rest of the file. A lone photo proves nothing.
Protection starts today
The 2026 enforcement landscape doesn’t reward whoever has the most invoices, but whoever can prove that each operation was real. The materiality file has stopped being a good practice and Hans become your first line of defense. Don’t wait for the request: start with your highest-value operations, turn it into a habit, and review it at every close. Assembling the evidence when the operation happens takes minutes; reconstructing it during and audit can cost millions.
Do it with DYNAMI
Building a file for each operation by hand becomes unfeasible when you handle hundreds of CFDI’s a month. DYNAMI does it for you: it links each receipt to its contract, its payment and its deliverables, safeguards then with a certain date, and alerts you when an operation is left without support. You arrive at any review with the file already assembled, not improvised.
Discover DYNAMI. Materiality Module. Schedule a demo with Cumbre Asesores.