What Is the Carta Porte and How Does It Work?

A truck loaded with goods leaves the plant headed for a customer in another state. Halfway down the highway, tax authority personnel stop the vehicle for a routine inspection and ask for the document covering the movement of those goods. The driver hands over the invoice, but the invoice is not enough: the rule requires a specific attachment with the origin, the destination, the goods being carried, and the means of transport. Without that attachment, the vehicle can be held for hours, the goods risk temporary seizure, and the carrier faces a fine that, depending on the severity, can represent a considerable share of the value of the load. All of it happens because the company assumed the product invoice was enough to cover the trip.

The carta porte is the SAT Complemento Carta Porte, an attachment to the CFDI that documents the movement of goods within Mexico, listing the origin, destination, goods, and transportation used, and it is mandatory for carriers and for companies with their own or contracted fleets.

The Risk of Moving Goods Without the Right Attachment

Many companies with their own fleet still treat moving goods as an internal formality, covered by a simple invoice or a delivery note, while the tax authority requires specific information about how, where, and in what those goods are moving. This confusion is most common in companies that until recently did not haul goods themselves and now run a fleet, distributors that started contracting out transportation, or manufacturing plants that ship directly to the end customer without going through a logistics intermediary.

The consequence of not carrying a valid attachment during a shipment is not limited to a fine. It includes the possibility that the goods are held while the administrative situation is resolved, which means lost delivery time, a customer waiting for an order that will not arrive on the committed date and, in some cases, the loss of the goods themselves if the product is perishable or has a short shelf life.

What Information the Attachment Requires About the Shipment

The Complemento Carta Porte brings together, in a single document linked to the CFDI, the data that identifies the shipment: the origin and destination locations with their tax addresses, a detailed description of the goods being carried including weight and quantity, the details of the means of transport (license plates, permit number, vehicle type) and, where applicable, the details of the driver and the carrier entity. This information allows the authority to verify, during a roadside inspection, that the goods physically in the vehicle match the ones covered by the tax document.

The reason this level of detail is required is that the carta porte does not document a sale, it documents the physical movement of goods across national territory, and that movement is what the authority needs to trace.

When the Attachment Is Mandatory

The attachment is mandatory whenever goods move by road, whether the owner of the goods hauls them on its own transportation or a carrier is contracted for the service. It applies both when the movement stays within the same state and when it crosses into another one, and it also covers foreign trade shipments for the portion of the trip that takes place within Mexico. The obligation falls on whoever moves the goods, not only on whoever sells them, so a plant shipping on its own fleet carries the same obligation as a company dedicated exclusively to transportation.

Pinpointing exactly which of your company's operations generate a shipment subject to this requirement is the first step before deciding how to automate issuing the attachment within your billing workflow.

Why Generating the Attachment Manually Increases the Margin for Error

When the attachment is created by hand, entry by entry, for every shipment, the margin for error grows with each piece of data someone transcribes from a paper delivery note or an email. A tax address entered incompletely, a description of goods that does not match the physical product, or an outdated license plate are errors that only surface during a roadside inspection, when it is already too late to correct them without consequence.

Automating the issuance of the attachment from data that already exists in your order and inventory systems removes the duplicate entry and ensures that the information on the tax document matches the goods actually leaving the warehouse.

Where the Carta Porte Attachment Is Most Often Overlooked

The risk of an incomplete attachment is not spread evenly across the operation. There are specific moments in the logistics flow where the odds of an error rise, because the shipment gets arranged outside the usual billing process.

Transfers Between a Plant and the Company's Own Distribution Center

When a company moves goods between its own plant and its own distribution center, it is common to assume that, since this is an internal movement with no sale involved, the tax requirement does not apply the same way. That assumption is wrong: a transfer between two locations of the same company also requires the corresponding attachment, because the obligation arises from the physical movement of goods by road, not from whether a commercial transaction is attached to it.

Companies that classify this type of transfer as low risk are frequently the ones that get flagged during an inspection, precisely because they did not consider it necessary to document the trip with the same care as a delivery to an end customer.

Last-Minute Contracted Transportation

When an urgent order exceeds the capacity of the company's own fleet and an outside carrier is hired the same day, the corresponding attachment often gets created after the vehicle has already left, under pressure to meet the committed delivery time. That inverted sequence, leave first and document afterward, is exactly the scenario a roadside inspection exposes, because the driver is not carrying a valid document at the moment of the check.

Fixing this requires that generating the attachment be part of the same flow in which the carrier is confirmed, not a later step that depends on someone remembering to do it.

A Change of Vehicle or Driver After the Document Is Issued

An attachment is issued with the details of a specific vehicle and driver, but in daily operations it is common for a company to reassign a trip to another vehicle after a last-minute breakdown or a driver's absence, without updating the corresponding tax document. That gap between what the attachment says and what is actually on the road is one of the most frequent inconsistencies an inspection catches.

A process connected to your dispatch operation detects the change of vehicle the moment it happens and regenerates the attachment before the truck leaves the yard, instead of letting the inconsistency travel along with the goods.

Why Integrating the Carta Porte Into Your Logistics Operation Lowers the Risk

When generating the Complemento Carta Porte is connected to your ERP, your WMS, and your TMS, the document is assembled from data you already captured when processing the order: goods, weight, route, assigned vehicle, and carrier. That drastically reduces the risk of a shipment hitting the road without the right tax backing, because the attachment is produced as a natural part of the dispatch process rather than as an extra formality someone can forget.

At Oasys we integrate ERP, WMS, TMS, and Production into a single platform running on our own servers in a data center, without depending on the public cloud, which lets carriers and fleet operators in sectors such as logistics, retail, distribution, manufacturing, and restaurants generate the attachment consistently for every shipment.

That consistency matters because compliance with the Complemento Carta Porte is not evaluated once a year, it is evaluated every time a vehicle is out on the road. A company can have the right process documented in an internal manual and still fail in daily execution if it depends on every employee remembering the manual step before dispatching. When the attachment is generated automatically as part of the order and dispatch flow, compliance stops depending on one person's memory and becomes part of the operation itself.

Frequently Asked Questions

Does the carta porte apply only to transportation companies?

No. It applies to any company that moves goods by road, whether on its own fleet or a contracted one, including manufacturing plants and distributors that ship directly to customers.

What happens if a shipment moves without a valid attachment?

The tax authority can stop the vehicle, hold the goods during the administrative review, and fine the company responsible for the shipment.

Can the attachment be generated automatically?

Yes. When your order, inventory, and transportation systems are integrated, the attachment is assembled from data that already exists in the operation, with no additional manual entry.