10 mistakes when implementing the DeCA (and how to avoid them before it is mandatory)

Many companies believe that adapting to the DeCA is a matter of no longer printing a document and saving it as a PDF. It is not. The rules that set out its characteristics —the Resolution of 5 June 2026 (BOE-A-2026-12784)— lay down specific requirements for generation, verification, access, retention and traceability. Failing any of them means not complying, however “digital” your document may look.

The DeCA (Documento electrónico de Control Administrativo) is the digital, mandatory version of the control document for domestic road freight transport in Spain, required ten months after Ley 9/2025 on Sustainable Mobility comes into force. If you need to go over exactly what it is and what it demands, the full explanation is here: how to meet the DeCA requirements with Slot’s Eyes.

With the requirements in mind, these are the mistakes we are going to see most often —and how to avoid them.

Mistake 1. Thinking a scan or an image in a PDF is enough

The most widespread mistake. The Resolution is blunt: the file must be natively generated in digital form, that is, structured data turned into a readable document. PDFs obtained by scanning a sheet of paper are not valid, and neither are digitised images. On top of that, the format is PDF no larger than 5 MB, and the creation and modification date and time must travel as metadata inside the PDF itself.

Turning your usual document into a PDF does not make you compliant: it leaves you exactly where you were, but with the false impression of being ready.

Mistake 2. Still typing in by hand data that already exists in the booking

This is the mistake that will cost the most time and the most errors, day after day. The application has to turn data into a document “as soon as it is known”, and in a dock operation much of that data already exists: carrier, plate, driver, goods, origin and destination, dates.

Typing it again is not just slow; it multiplies the risk of error in a document that now carries administrative control value. This is where Slot’s Eyes fits in: the DeCA lives inside the booking and is born pre-filled with what your operation already knows, so the operator only completes what is missing. We go into it in detail in the article on automating the DeCA with the booking data.

Mistake 3. Generating the document too late

The rules require the file to be generated before the service actually starts, and the application to record the creation date and time precisely to prove it came before the transport. On top of that, a copy has to be handed to the driver before setting off, on the phone or printed, and with the QR code.

Leaving generation for “when the truck is already on its way” fails from the outset. The correct process has a clear point of issue before departure, not a document completed along the way.

Mistake 4. Not providing proper verification with a QR code and URL

The file must include, inside the PDF itself, a QR code pointing to the document’s unique web address (URL). That is how, during an inspection, the officer reaches the genuine DeCA. A document with no QR code, or with one that does not resolve to a valid URL, leaves verification lame at the very moment of the check.

👉 You can see how a DeCA should look with PDF, QR code and verification working.

Mistake 5. Building a URL that asks for credentials or manual steps

A detail many will overlook. The URL must start with https:// (TLS 1.2 or higher) and, when invoked, download the PDF directly. The Resolution expressly forbids the URL leading to a page that asks for a username and password, or that includes buttons or other elements requiring manual interaction.

You can protect the link with encryption, tokens or an expiry date, as long as it does not expire before the service ends and does not block the direct download. Seven calendar days after completion, you may indeed switch the download off. The typical mistake will be building a portal with a login “for security”: that, precisely, does not comply.

Mistake 6. Not keeping the document properly

The rules require the files to be kept for at least one year, and this applies both to the contractual shipper and to the actual carrier (each may have its own repository; it is enough that both can download them during that year). The repository domain is free and does not have to be reported.

Saving the PDF “in some folder” without guaranteeing it will be available for a year, or assuming the other party is already keeping it while you have no access, is a silent breach that only surfaces when somebody asks for the document.

Mistake 7. Not recording changes properly (and writing notes by hand)

This deserves precision, because it is where most of the confusion sits. If the DeCA has to be modified during the service, the Resolution accepts two valid methods: modifying the same PDF —adding the new data and the reason, and keeping the old data marked as invalid, in which case the URL and the QR code do not change— or generating a new PDF with a new URL and QR code, keeping the original for traceability. In both cases the updated document has to reach the driver.

What is not acceptable is correcting the printed copy in pen: handwritten notes are not taken into account. The mistake is improvising changes outside those two routes and losing the traceability the rules set out to protect.

Mistake 8. Treating the DeCA as a module isolated from the operation

The strategic mistake. Many companies will buy a tool separate from their dock system and start typing into it data they already hold in their bookings. The result is duplicated work, day after day.

If your operation already handles bookings, plates, carriers and goods, the DeCA should feed on that information rather than ask for it again. That integration is the difference between an obligation that slows you down and one you barely notice. Before deciding, it is worth measuring your starting point with a DeCA readiness checklist.

Mistake 9. Not naming internal owners or setting up a test run

Implementing the DeCA is not just picking software. You have to decide who generates the document, who validates it, who handles an incident on the road and with what permissions. Without clear owners, the document is generated late, badly, or not at all.

Just as important: test with real cases before the mandatory date. One end-to-end trial shipment —generation, handover to the driver, QR verification, a modification— reveals the flaws while there is still room to fix them.

Mistake 10. Leaving team training to the last minute

Even with the tool ready, compliance happens at the dock and in the cab. If the operator does not know how to issue the DeCA before departure, or the driver cannot show the QR code during an inspection, the system fails at its most visible point.

Leaving training for September turns the roll-out into a race against the clock. Training in advance, with the process already tested, is what separates a calm transition from an emergency.

An action plan to avoid these mistakes

A sensible order to get there in time:

• Identify which transports affect you (domestic and cabotage; international ones are out of scope).
• Find where the document’s data already lives and avoid typing it again.
• Make sure generation is natively digital, with a PDF of 5 MB or less, a QR code and a direct download URL.
• Check that the URL asks for no credentials and that the document is kept for a year.
• Name the owners, run a full trial shipment and train the team.

Conclusion

If your company already manages dock bookings, plates, carriers and goods, much of the DeCA information already exists. The key is not to type it in again, and to generate the document meeting every requirement: native PDF, QR code, direct download URL, one-year retention and traceability of changes.

Avoiding these ten mistakes means, in practice, having the DeCA sorted before it becomes mandatory.

👉 Get your operation ready for the DeCA and book a Slot’s Eyes demo

This article is for information only and does not constitute legal advice. For the regulatory detail, see the Resolution of 5 June 2026 (BOE-A-2026-12784) and Ley 9/2025, of 3 December, on Sustainable Mobility.