About this plugin
Polish B2B customers need an invoice, and an invoice needs the buyer NIP (the Polish tax ID). This plugin collects that data in WooCommerce checkout, checks the NIP checksum before the order is placed, shows the NIP as a column in your order list, and exports the whole set to CSV for your accountant.
Works in both checkouts: classic and block
0 the fields appear in the classic checkout (shortcode) and in the block checkout (Cart & Checkout Blocks, the default in new WooCommerce installs). The plugin declares cart_checkout_blocks compatibility, so WooCommerce no longer shows an incompatibility warning. Both paths write exactly the same order data, so the NIP column and the CSV export do not care which checkout your store uses.
NIP validation without calling anyone
The NIP is checked locally: length, format and the 10-digit checksum. The plugin never sends the number anywhere. No VIES lookup, no whitelist API, no SDK, no telemetry, no external HTTP request of any kind.
Zero outbound calls is a deliberate design decision, not a missing feature.
CSV export for your accountant
The WooCommerce > KSeF/NIP Export screen downloads recent orders as CSV: order number, date, status, whether the customer asked for an invoice, NIP, NIP validation status, company name, billing email, e-invoice email, total and currency. Open it in a spreadsheet or hand it to your accounting office.
What this plugin does NOT do
It does not issue invoices, does not generate the FA(3) XML structure, does not connect to the KSeF API, does not authenticate with a certificate and does not download official confirmations. It is a tool for cleaning up invoice data before it reaches accounting, not an invoicing application.
The plugin adds:
- A company invoice checkbox in checkout (classic and block).
- A Polish NIP field with checksum validation.
- An optional e-invoice email field.
- Order meta for invoice request, NIP, e-invoice email, and validation status.
- A NIP column in WooCommerce order lists (legacy and HPOS).
- A WooCommerce > KSeF/NIP Export page for recent order CSV export.
The plugin stores data locally in WooCommerce order meta. It does not call external APIs, does not send data to KSeF, and does not include tracking scripts.
Yzukar B2B Invoice Fields for KSeF is a workflow and data-cleanup tool. It does not provide legal, tax, accounting, or KSeF compliance advice and does not guarantee compliance with any law, schema, tax process, platform rule, or accounting requirement.
Documentation and the optional add-on
tech: guides on the NIP field, checkout validation and CSV export for accounting, an FAQ, and a free KSeF readiness pack (spreadsheet with an FA(3) field map, a printable checklist and starter CSV templates, all in Polish). org and is not required for anything this plugin does.