With the EU–Mercosur transitional arrangement now in force, companies trading with Argentina, Brazil, Paraguay and Uruguay can benefit from reduced tariffs – provided they meet the formal requirements and can properly evidence the origin of their goods.
Customs declarations will need the correct preference and document codes, including U126 for origin documentation. New markings linked to the Mercosur region will also apply. On paper, the system looks clear. In day-to-day operations, it may prove far more demanding.
Claiming preference after clearance: you have two years
A key change is that importers can request preferential tariff treatment even after the goods have been imported. If the preference wasn’t claimed at the time of clearance, it can still be requested later – up to two years from the import date. This is particularly useful when origin paperwork arrives late, needs corrections, or when goods have been under special procedures, such as a customs warehouse.
That said, businesses shouldn’t treat this option as a safety net that allows origin matters to be postponed. Amending declarations after the fact typically increases the likelihood of checks and follow-up questions from customs.
Mercosur countries are not following one model
One of the biggest surprises for the market may be that Mercosur states have not implemented a single, uniform approach to proving origin.
Some countries will accept two types of origin evidence, while others will accept only one. Argentina, Brazil and Uruguay allow both a standard exporter statement and a transitional form of a “certificate of origin”. Paraguay, for now, is applying only the certificate-based solution.
This may sound like a technical detail, but it can have very real consequences.
If an importer provides the wrong type of document for goods originating in Paraguay, customs may refuse to grant the preferential rate.
In practice, this can mean:
• additional duty payable,
• interest charges,
• the launch of a verification procedure,
• longer clearance times.
Less flexibility in origin paperwork
The new framework significantly tightens documentary requirements.
Exporters in Mercosur countries will have to use specific identification numbers, such as:
• CUIT – Argentina,
• CNPJ – Brazil,
• RUT – Uruguay.
Customs authorities may verify these numbers using national electronic registers.
Origin labelling rules are just as important. Documents should refer to origin in broad terms as “European Union” or “Mercosur”. Specific countries – such as Poland or Brazil – should not be named. It’s a small point, but in practice it can be enough for the documentation to be challenged.
Extra care for goods in transit and in warehouses
The agreement also includes transitional rules for goods that, when the provisions took effect, were already in transit, held in customs warehouses, or located in free zones. Preferential treatment can still be applied for up to six months from the start of the agreement’s application.
Operationally, this means closer control is needed for sea freight imports and for goods moving under special procedures.
Origin documents as a risk management tool
For years, origin documents were often treated as a box-ticking exercise added at the end of the logistics chain. The EU–Mercosur rules make it clear that customs will approach this differently.
The risk isn’t limited to whether the product truly qualifies as originating. Controls may also cover document consistency, exporter number accuracy, use of the correct templates, and whether invoices, commercial paperwork and the customs declaration align. For many companies, putting in place pre-clearance checks for origin documentation may become not just good practice, but a practical way to reduce customs risk.
What importers should take away
The EU–Mercosur agreement creates an opportunity to secure preferential duty rates, while also raising the bar on documentation and compliance. In practice, success will depend not only on understanding the origin rules, but on using the right documents and accounting for differences between Mercosur countries. Under the new regime, even a seemingly minor formal error can result in preference being denied, additional amounts becoming due, and increased scrutiny from customs.
About the author:
Dr. Izabella Tymińska, customs expert, specialising in customs law and foreign trade. She provides advisory services on customs regulations, the import and export of goods and services, and the financial and economic analysis of international contracts. She focuses on complex, non-standard cases. She is a former long-term employee of the Customs Office. Over many years she has worked with logistics and forwarding companies, including in board-level roles. She lectures at the War Studies Academy in Warsaw, within the Institute of Logistics at the Faculty of Management and Command. She has also taught at ALMAMER University in Warsaw, the Higher School of Customs and Logistics, and the University of Technology and Economics. She is a graduate in Economics, Logistics, International Relations, Management, and Defence Economics.
