Additional KSeF Data Through Stripe Metadata

S2K automatically retrieves data from your Stripe invoices and sends it to KSeF. Some KSeF fields, such as GTU code, PKWiU, or buyer contact details don't have a direct equivalent in Stripe, but you can set them through metadata in customer and product objects.

How Stripe Metadata Works

Metadata are key-value pairs that you can add to almost any object in Stripe: customer, product, invoice. S2K reads selected keys and passes them to corresponding fields in the KSeF structure. Keys follow the format s2k_{field}, e.g., s2k_gtu or s2k_contact_email. If a key doesn't exist in the metadata, S2K simply skips that field.

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Buyer Data (Customer Metadata)

Set the following fields on the Customer object in Stripe (Customers → selected customer → Metadata).

Metadata Key	KSeF Field	Description
s2k_custom_client_id	Podmiot2/NrKlienta	Your own customer number used in contract or order
s2k_gv	Podmiot2/GV	true if buyer is a VAT group
s2k_jst	Podmiot2/JST	true if buyer is a local government unit
s2k_contact_email	Podmiot2/DaneKontaktowe/Email	Buyer's email on the invoice
s2k_contact_phone	Podmiot2/DaneKontaktowe/Telefon	Buyer's phone on the invoice

Example

1. Go to Stripe Dashboard → Customers → select customer
2. Scroll to Metadata section
3. Add keys:
   • s2k_custom_client_id → KL-2024-001
   • s2k_contact_email → [email protected]

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Product Data (Product Metadata)

Set the following fields on the Product object in Stripe (Product catalog → selected product → Metadata).

Metadata Key	KSeF Field	Description
s2k_gtu	FaWiersz/GTU	GTU code (e.g., GTU_01, GTU_12)
s2k_pkwiu	FaWiersz/PKWiU	Polish Classification of Products and Services symbol
s2k_gtin	FaWiersz/GTIN	Global Trade Item Number (EAN/barcode)
s2k_cn	FaWiersz/CN	Combined Nomenclature symbol (foreign trade)
s2k_pkob	FaWiersz/PKOB	Polish Classification of Construction Objects symbol

Example — Setting GTU Code

1. Go to Stripe Dashboard → Product catalog → select product
2. Click Edit
3. Scroll to Metadata section
4. Add key s2k_gtu with value e.g., GTU_12
5. Save

From now on, every invoice containing this product will have the GTU code populated in KSeF.

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GTU Codes — List of Values

Code	Category
GTU_01	Alcoholic beverages
GTU_02	Excise goods (fuels, oils, etc.)
GTU_03	Heating oil
GTU_04	Tobacco products, dried tobacco
GTU_05	Waste — only those specified in regulations
GTU_06	Electronic equipment, parts for them
GTU_07	Motor vehicles
GTU_08	Precious and non-precious metals
GTU_09	Medicines, medical devices
GTU_10	Buildings, structures, land
GTU_11	Gas and energy services
GTU_12	Intangible services (IT, consulting, finance, etc.)
GTU_13	Transport and forwarding services