What changes from the proforma
The commercial invoice is the proforma turned into fact. Same content, different status: this one is numbered in your sales series, it is booked, it is declared, and it is what customs at destination uses to work out what your customer pays.
So the test is not “resembling” the proforma, it is matching it. If quantity or price changed between offer and invoice because the order changed, you issue a new proforma before invoicing. Invoicing something different from what was quoted is the fastest way to have a letter of credit fall over or a customs authority ask for explanations.
The other difference is fiscal: an export out of the European Union is invoiced without VAT, and that exemption has to be provable.
What it adds to the proforma
Every proforma field is still there. These are the ones that appear or change when you invoice for real.
- Invoice number
- From your normal sales series, consecutive and with no gaps. It is what makes it an accounting document.FC-2026-0312
- Issue date
- The tax point of the transaction. It sets the period in which it is declared.16/09/2026
- VAT exemption wording
- The invoice carries no VAT, but it has to say why. The exact wording depends on whether it is an export or an intra-EU supply, and on your Member State’s own rule.VAT exempt — Art. 146 Directive 2006/112/EC (export of goods)
- Customer’s VAT numberOptional
- Only on sales to another Member State, and checked in VIES on the day of the transaction. Without a valid VAT number, the supply is not exempt.SE556789012301
- Reference to the proforma
- The number of the offer it comes from. It is what lets your customer and their bank match the documents.Ref. proforma PRO-2026-0147
- Reference to the customer’s orderOptional
- Their purchase order number. Without it, an invoice can take weeks to be approved in a large company.Your order PO-88213
- Statement on originOptional
- If there is a trade agreement and you meet the origin rule, the text of the statement on origin goes here, with your REX number where applicable.The exporter of the products covered by this document (REX ESxxxxxxxxx) declares that, except where otherwise clearly indicated, these products are of European Union preferential origin.
- Breakdown of Incoterm costsOptional
- If the price includes freight or insurance, break them out. Customs needs to know which part is goods in order to work out the customs value.Goods €23,280.00 · Freight €1,420.00 · Insurance €96.00
- Signature or stampOptional
- Not required in the Union, but some destinations and banks insist on it. Asking beforehand saves a resend.Signed and stamped
Why customs does not charge on your invoice
Duty is not calculated on the amount your invoice shows, but on the customs value, which is a different thing. It starts from the price paid and adds items that are not always invoiced: transport and insurance up to the border, packaging, royalties, or the value of materials the buyer supplied to you free of charge.
Which is why the Incoterm breakdown matters. If you sell CIF, the price already includes freight and insurance to the port of destination, and in many destinations the leg after the border has to be deducted so no excess duty is paid. With a lump-sum price that adjustment cannot be made and your customer overpays.
Before issuing it
- It matches the proforma in quantity, price, Incoterm and description
- It carries the VAT exemption wording that fits the transaction
- If it is intra-EU, I checked the customer’s VAT number in VIES today
- Weights and package counts are the same as on the packing list
- If I am claiming preferential origin, I meet the rule and can prove it
- I have agreed with the forwarder that they will send me the exit confirmation
The ones that get expensive later
- Invoicing a European customer without VAT and without checking their VAT numberIf the number was not active on the date of supply, the transaction stops being exempt and you end up paying the VAT yourself, with a surcharge.
- Not keeping the exit confirmationIt is the only proof the goods left the territory of the Union. Without it the exemption does not hold up in an inspection.
- Issuing an invoice that differs from the proformaIf there is a letter of credit, the bank compares and rejects. If there is not, customs at destination finds two documents that do not agree.
- Quoting a lump-sum price under CIF or DAPWithout breaking out transport, your customer cannot deduct the leg after the border and pays duty on amounts they should not.
- Copying a statement on origin from another supplierYou sign the statement and you answer for it. If your product does not meet the origin rule for its heading, customs at destination can claim the duty years later — from your customer, who will claim it from you.