Connecting KSeF to your stack: APIs, webhooks, ERPs and billing tools, with working examples.
Building a KSeF integration yourself means generating FA(3) XML, authenticating to KSeF, sending encrypted invoices and polling their status; using a KSeF API means you send plain JSON and the provider owns the rest. For most SaaS and e-commerce teams, an API like Notaly is faster and cheaper to ship and maintain. Build your own only if you already run a full e-invoicing stack and need maximum control.
Retrying a timed-out KSeF submission blindly can create a duplicate invoice, because the request may have reached KSeF even though you never saw the response. The safe pattern is to attach a stable idempotency key on your side to every submission, check the invoice's status against KSeF before resubmitting, and only resubmit when you are certain no earlier attempt succeeded.
A KSeF token is an authentication credential with a validity period, and when it expires your integration can no longer open sessions or submit invoices. The routine that keeps you running is simple: check the expiry date, generate a new token before the old one dies, and replace it in one place — Connect KSeF in Notaly.
A WooCommerce or Shopify store can issue KSeF invoices through a plugin or through a KSeF API such as Notaly's, which turns each order into a FA(3) invoice and submits it automatically. You do not need to write FA(3) XML or run your own KSeF integration. For most stores the API route is the fastest way to add e-invoicing without a Poland-specific engineering project.
Create a sandbox account: API key in seconds, 3 free test invoices on KSeF TEST, no credit card.
