How to Prepare a Proforma and Commercial Invoice: An Exporter’s Checklist

In an export shipment, almost everything, from the customs declaration and certificate of origin to the freight quote and insurance, relies on what the invoice says. A small mistake can mean delays at customs, problems for the buyer when paying duties, or losing preferential tariff treatment. This guide explains how to prepare a proforma invoice and a commercial invoice, what information is mandatory, and how export invoices are issued as e-invoices in Turkey.

Proforma invoice vs commercial invoice

A proforma invoice is a quotation and advance information document sent to the buyer before the sale is final. It shows the description, quantity, price and delivery terms of the goods. The buyer may use it to confirm the order, open a letter of credit, apply for an import licence or arrange a foreign currency transfer. It is not a tax invoice and is not booked in the accounts.

A commercial invoice confirms that the sale has taken place and is the document that counts for tax and customs purposes. The value, quantity and description in the customs declaration must match it, and the customs authority at destination will largely calculate duties on the value it shows.

A practical rule: treat the proforma as a draft of the commercial invoice. If price, quantity or delivery terms change between the two, tell the buyer and, especially under a letter of credit, the bank in advance.

Mandatory information on a commercial invoice

Destination countries may ask for extra details, but international practice expects at least the following:

Seller and buyer details: Company name, full address, tax number, and the buyer’s registration number at destination where required (for example an EORI number in the EU).
Invoice number and date: Other documents and the customs declaration refer to it.
Clear description of the goods: A commercial description covering material, purpose and model, rather than vague wording like “spare parts”.
HS code (GTİP in Turkey): The tariff classification of the goods.
Quantity and unit: Pieces, kilograms, metres, sets and so on.
Unit price and total value: With the currency.
Delivery term (Incoterm): The rule and the named place, for example “FCA Istanbul Incoterms® 2020”.
Country of origin: Where the goods were produced.
Gross and net weights and number of packages: Including cartons, pallets or crates.
Payment terms: Advance payment, cash against documents, letter of credit, etc.
Transport details: Mode of transport, loading and destination port or place, and the bill of lading or CMR number if known.

A detailed packing list completes the invoice by showing contents, weights and dimensions per package.

HS code, origin and weights: where mistakes happen most

HS code

Turkey’s tariff code, the GTİP, places your product in the customs tariff. The first six digits follow the international Harmonized System and are the same worldwide; further digits vary by country. Turkish export declarations use a 12-digit GTİP. Your buyer’s country may use its own longer code, so at the very least the 6-digit HS code on the invoice must be right. If you are unsure about classification, check with your customs broker.

Origin

Origin is the goods’ “economic nationality”: not the country they are shipped from, but the country where, under the rules, they were produced or sufficiently processed. Goods shipped from Turkey but manufactured elsewhere should show that other country as origin. To claim preferential duty, the origin on the invoice and on the proof of origin must match.

Weights

Net weight is the weight of the goods without packaging; gross weight includes packaging. Weights on the invoice, packing list, bill of lading or CMR should all agree. For the chargeable weight used in freight pricing, our freight calculator can help.

How to state the Incoterm and the currency

The Incoterm shows where costs and risk pass from seller to buyer, and it must always be written with the rule and the place. “FOB” alone is incomplete; “FOB Port of Mersin Incoterms® 2020” is correct. If you are not sure which rule fits, try our Incoterms selection tool.

State the currency clearly at the top of the invoice or next to every amount (EUR, USD, TRY, etc.). Invoices to foreign buyers usually use the contract currency. For converting to Turkish lira in your tax records and which exchange rate applies, ask your accountant.

Some countries want freight and insurance shown separately so that the customs value can be calculated correctly. Under CIF or CIP sales, listing goods value, freight and insurance on separate lines reduces questions at destination.

Export invoices and e-invoicing in Turkey

In Turkey, export invoicing runs on a shared infrastructure between the Revenue Administration (GİB) and the Ministry of Trade. Under Tax Procedure Law General Communiqué No. 509, taxpayers registered for e-invoicing must issue invoices for goods exported under a customs declaration as e-invoices (as of October 2026).

Key points:

The invoice is issued with the “Export” (İhracat) type. Alongside the foreign buyer, the Ministry of Trade appears in the recipient field, and the invoice goes to the Ministry through the system rather than directly to the buyer.
Customs fields such as the HS code, delivery term, mode of shipment and package details must be completed for each line.
Invoice data feeds into the customs declaration and must be consistent with it. A printout or PDF of the invoice is sent to the buyer.
Service exports, micro exports declared with an ETGB (electronic commerce customs declaration) instead of a standard customs declaration, and proforma invoices fall outside this requirement. For micro export parcels, an e-archive invoice is usually issued to buyers who are not e-invoice users.

Thresholds and technical rules for e-invoicing change from time to time, so follow GİB announcements and your accountant for the current position.

Before issuing the invoice, check the HS code, delivery term and package details with the customs broker who will prepare the export declaration. Corrections after the declaration is registered take time.

Checklist for proforma and commercial invoices

Do the buyer’s name and address match the contract, the letter of credit and the bill of lading?
Is the description clear enough for a customs officer?
Is the HS code correct, and is origin shown for each line?
Are the Incoterm, place and version (Incoterms® 2020) stated?
Do gross and net weights match the packing list and transport document?
Are the currency and total clear, with any discount or advance payment shown?
Does the destination country require a signature, a specific statement or extra data?

Frequently asked questions

Can goods clear customs on a proforma invoice?

As a general rule, no. A proforma is a pre-sale quotation; customs procedures rely on the commercial invoice. Special cases such as free samples may be handled differently, so check with your customs broker.

Is the HS code mandatory on the invoice?

On export invoices issued as e-invoices in Turkey, the HS code field must be completed. On paper or PDF commercial invoices we still recommend including it, because it makes the destination customs’ job easier.

Which currency should I invoice in?

Usually the currency agreed in the sales contract. Ask your accountant about the exchange rate and conversion rules for your tax records.

What if the invoiced weight differs from the weighed weight?

Small differences are usually tolerated, but large ones can trigger inspection and corrections to transport documents. Weighing before loading and preparing documents accordingly is the safest approach.

A well-prepared invoice speeds up everything that follows. When Medius plans your transport, we also review your documents and work with your broker on customs clearance coordination. If a term is unfamiliar, see our logistics glossary, or reach us through our quote form.