CONTPAQi: DIOT Error — How to Fix Mexico's Monthly Tax Declaration

TL;DR — Quick Summary

Fix DIOT generation errors in CONTPAQi: invalid supplier RFC, VAT entries without third-party assignment, and text file format issues for Mexico's SAT portal.

DIOT Generation Errors in CONTPAQi

The DIOT is a mandatory monthly tax filing in Mexico that requires businesses to report purchase operations and VAT paid to each supplier. Generating this file from CONTPAQi often produces errors that prevent successful upload to the SAT portal.

This article covers the most common error causes and step-by-step solutions.

Prerequisites

CONTPAQi Contabilidad (version 14.x or higher) or CONTPAQi Comercial updated to the latest Service Pack.
Supplier catalog with valid, complete RFCs (tax IDs).
Journal entries for the reporting month fully captured and reviewed.
Access to the SAT portal with a valid e.firma or password.

Common Error Causes and Solutions

1. Invalid or Incomplete Supplier RFC

The most frequent DIOT error is that one or more suppliers have an incorrect RFC in the CONTPAQi catalog.

Problem	Example	Solution
RFC with spaces	`ABC 120315 LK7`	Remove spaces: `ABC120315LK7`
Incomplete RFC	`ABC12031`	Complete to 12/13 characters
Misspelled generic RFC	`XAXX01010100`	Correct to `XAXX010101000`
Foreign supplier without RFC	(empty)	Use `XEXX010101000`

2. VAT Entries Without Third-Party Assignment

If a journal entry has VAT account movements but no third party (supplier) assigned, CONTPAQi cannot include that operation in the DIOT.

Fix: Edit journal entries for the month, filter VAT accounts, and assign the correct supplier to every VAT line item.

3. Incompatible File Format

The SAT periodically updates the DIOT schema. Older CONTPAQi versions may generate an outdated format that the portal rejects. Update CONTPAQi to the latest Service Pack.

Pre-DIOT Validation Checklist

#	Check	Where	Expected
1	All suppliers have valid RFC	Catalogs → Suppliers	12 or 13 chars, no spaces
2	VAT entries have supplier assigned	Journal entries	Every VAT line has a third party
3	VAT withholdings separated	Journal entries	Separate account for withheld VAT
4	CONTPAQi updated	Help → About	Latest Service Pack
5	DIOT total = Monthly VAT return total	DIOT report vs DPIVA	Amounts match

Summary

Assign third parties to every VAT entry at capture time, validate supplier RFCs before the first invoice, and compare DIOT totals with your monthly VAT return before uploading to the SAT.

Guide & Instructions

Estimated Time: 30m

Tools Needed:

CONTPAQi Contabilidad or Comercial
Updated supplier catalog
SAT portal (declarasat.sat.gob.mx)

Verify supplier catalog

Open CONTPAQi > Catalogs > Suppliers. Check each supplier's RFC: it must be 12 characters (legal entity) or 13 (individual). Remove leading/trailing spaces. Use XAXX010101000 for general public; XEXX010101000 for foreign suppliers.

Review VAT accounting entries

Go to the journal entries for the month. Filter for entries with VAT accounts (account 1180 or equivalent). Verify each VAT entry has a third-party (supplier) assigned.

Generate the DIOT from CONTPAQi

In CONTPAQi go to Reports > DIOT. Select the period, verify the data, and click Generate. The system creates a .txt file compatible with the SAT portal.

Validate the file before uploading

Open the .txt file in a text editor. Verify RFCs are correct, amounts match your monthly VAT return, and there are no empty lines or strange characters.

Upload to the SAT portal

Log in to declarasat.sat.gob.mx with your e.firma or password. Select DIOT, upload the .txt file. If rejected, check the specific error message — it usually indicates the line number with the problem.

Frequently Asked Questions

What is the DIOT and what is it used for?

The DIOT (Declaración Informativa de Operaciones con Terceros) is a monthly tax obligation in Mexico where businesses report VAT paid and withheld from suppliers to the SAT (tax authority). It is filed as a text file (.txt) generated by accounting software and uploaded to the SAT portal.

Why is my DIOT file rejected by the SAT portal?

Common reasons include: invalid or generic supplier RFC (tax ID), accounting entries with VAT but no supplier assigned as third party, VAT amounts that don't match stamped CFDI invoices, or an incompatible .txt file format for the current DIOT schema version.

How do I fix suppliers without a valid RFC for the DIOT in CONTPAQi?

Go to Catalogs > Suppliers in CONTPAQi. Open each supplier and verify the RFC has 12 or 13 valid characters (no spaces). Use XAXX010101000 for general public operations and XEXX010101000 for foreign suppliers. Save and regenerate the DIOT.

How often must the DIOT be filed?

The DIOT is filed monthly, no later than the 17th of the following month. If the 17th falls on a non-business day, the deadline extends to the next business day. The SAT can impose fines of $10,000 to $20,000 MXN for omission or late filing.