EORI, REX and the commercial invoice: the minimum paperwork to export outside the EU

Exporting outside the EU for the first time feels like a wall of acronyms. In practice a Spanish SME needs a short list: an EORI number, a commercial invoice that says the right things, a packing list, an export declaration lodged with the Spanish tax agency and, only when the destination has a trade agreement with the EU, a proof of origin, which above €6,000 may require REX registration. This guide goes through each one, with the source and the date we checked it.

EORI: your customs identity in the EU

The EORI number (Economic Operators Registration and Identification) identifies your company in every customs operation in the European Union: it goes on the export declaration, on the invoice and on the proof of origin. In Spain it is assigned by the Agencia Tributaria (AEAT) and takes the form "ES" followed by your NIF. Many Spanish companies already have one, because the AEAT registers operators that have carried out customs operations ex officio; if yours has not, or if your NIF starts with N, M, X or Y, you request it through the AEAT's electronic office under "Aduanas", with a digital certificate or Cl@ve. The AEAT's page on who must register lists no fee for the number (AEAT, Registro e identificación de operadores económicos (EORI), verified 22 October 2026). You can check whether a number is already active in the European Commission's EORI validation tool. Get this before anything else: the declarant of a Spanish export declaration must hold an EU EORI.

REX and the €6,000 threshold

REX (Registered Exporter System) is the EU database of exporters authorised to declare the preferential origin of their goods themselves, on the invoice, in the agreements that use it. The rule, verified 22 October 2026: for a consignment of EU-originating goods worth €6,000 or less, any exporter may make out the statement on origin on the invoice without being registered; above €6,000, the exporter must be registered in REX and quote its REX number in the statement (European Commission, REX system on Access2Markets; AEAT, Registro de Exportadores Registrados (REX)). In Spain you apply to your regional customs office through the AEAT's electronic office, using the form in Annex 22-06 bis; once registered you receive your REX number and the date from which it is valid.

Two things people get wrong. First, REX is not required for every destination: it is the mechanism of newer agreements such as CETA with Canada and of the GSP; older agreements, including the EU–Mexico and EU–Israel ones, use a EUR.1 movement certificate or an invoice declaration, and above €6,000 the status needed there is "approved exporter", granted by customs, not REX. Second, REX is only about origin. You still need an EORI, and registering in REX does not make goods originate in the EU: that depends on the product-specific rules of each agreement, and a wrong origin statement is your liability, not the carrier's.

The commercial invoice

This is the document customs on both sides read first. It must be a real invoice for the sale, not a pro forma, and should contain:

Undervaluing the goods "to save your customer duty" is the error that costs most: it is the importer who is penalised, and the goods are held.

The packing list

The packing list describes the shipment physically: how many boxes or pallets, their dimensions, gross and net weight per package, and which items are in which package. It lets the carrier calculate the volumetric weight, lets customs inspect one box instead of the whole pallet, and lets your customer check what arrived. It does not carry prices. If the goods come to us unpacked, we prepare it together with the packing or palletizing.

The export declaration (DUA / EX-A)

Every consignment leaving the EU customs territory from Spain needs an export declaration lodged electronically with the AEAT through its export system (AES). The declarant must hold an EU EORI and a NIF registered with the AEAT; when the declarant is not the exporter, it acts as the exporter's indirect customs representative (AEAT, Exportación, verified 22 October 2026). Once customs confirms the exit of the goods, the accepted declaration is your proof of export: your accountant uses it to justify the VAT exemption on the export sale, so keep it with the invoice. In our service, we prepare the export documentation with the details you give us and coordinate its lodging with the carrier; you do not file anything yourself, and if customs needs an extra piece of data, we ask you for it.

Proof of origin: only where an agreement exists, and only if your goods qualify

A certificate or statement of origin lowers your customer's duty only when the EU has a trade agreement in force with their country and your goods meet its rules of origin. Status by destination, verified 22 October 2026:

• Mexico. The EU–Mexico Global Agreement has applied to trade in goods since 2000. Proof is a EUR.1 certificate or an origin declaration on the invoice; any exporter may make the declaration up to €6,000, above that only an approved exporter; the proof is valid for 10 months (European Commission, EU–Mexico Global Agreement). A modernised agreement was signed on 22 May 2026; the European Parliament consented on 8 July and the Council concluded the interim trade agreement on 14 July 2026, but at the time of writing we have found no confirmation that Mexico's Senate has completed ratification, so the 2000 rules apply until the new text enters into force.
• Canada. CETA has applied provisionally since 21 September 2017; 17 EU member states have ratified it and 10 have not, but the trade chapters apply (European Commission, EU–Canada agreement). Proof is an origin declaration on the invoice; above €6,000 your REX number is required.
• Israel. The EU–Israel Association Agreement has been in force since June 2000 (European Commission, EU trade with Israel). Proof is a EUR.1 or an invoice declaration; above €6,000, approved-exporter status.
• Australia. Negotiations concluded on 24 March 2026, but the agreement is not signed, not ratified and not in force (European Commission, EU–Australia trade agreement). Until then, the normal (MFN) rates apply and no EU proof of origin lowers them.
• United States. No agreement. Origin is declared and marked, but it does not reduce duty, and the $800 de minimis exemption has been suspended since 29 August 2025 (CBP).

Some customers also ask for a non-preferential certificate of origin issued by a Chamber of Commerce; it does not lower duty but may be required by the buyer's bank or regulator. Tell us if your customer asks for one.

What we do

For companies in Spain, we take the shipment from your door to your customer's: we collect at your warehouse or office, or you bring the goods to our warehouse; we pack or palletize if needed; we prepare all the export documentation with the details you give us; we fly boxes and pallets; and we deliver door to door. Import duties and taxes at destination are paid by the receiver. We coordinate carriers and warehouses and work with the customs agent at destination; we are not a customs broker, and the customs information above is for planning, not advice. Lithium batteries, perfume, aerosols and chemicals can fly too: we run the dangerous-goods process in Spain and a DG specialist quotes the repacking. We reply within 24 business hours.

See also: export from Spain to the USA, export from Spain to Mexico, export from Spain to Canada and dangerous goods by air from Spain.