ksefujto
Free skills for your AI assistant

Describe the invoice. Get the KSeF file from your AI assistant.

Two free skills for your AI assistant. Give it a PDF or a few sentences and it prepares an FA(3) invoice for KSeF (Poland's National e-Invoicing System). If you make a mistake, it walks you through the correction.

Install for freeView on GitHub

How it works

  1. Describe the invoice

    Attach a PDF, paste the details, or just say in plain words who you're invoicing and for what.

  2. Your assistant prepares the file

    You get an XML file in the FA(3) format that KSeF requires.

  3. Check it and send it

    Drop the file into our validator, then send it to KSeF, for example through the KSeF Taxpayer App (Aplikacja Podatnika KSeF).

One issues, the other corrects

ksef-invoice

New invoice

Turns details from a PDF, a message or a form into an XML file for KSeF.

  • Domestic sales
  • Reverse charge for buyers in and outside the EU
  • Intra-Community supply of goods (WDT) and exports
  • VAT exemption and the margin scheme
  • Advance invoices
ksef-correction

Corrective invoice

Guides you step by step through issuing a corrective invoice.

  • Correcting a standard invoice (KOR)
  • Correcting an advance invoice (KOR_ZAL)
  • Correcting a final settlement invoice (KOR_ROZ)
  • A wrong buyer NIP, which takes two documents to fix

How to install

Pick the assistant you use. You only install the skills once.

AI coding assistants

Run one command in your terminal. It detects your assistant (Claude Code, Codex, Copilot and others) and installs both skills. Requires Node.js.

npx skills add ksefuj/skills

Claude.ai and the desktop app

  1. Download the .skill files from GitHub (the Releases tab).
  2. Open Claude's settings and go to the Skills section.
  3. Upload both files.
Download the files

Claude Code plugin

Prefer a plugin? Run these two commands in Claude Code:

/plugin marketplace add ksefuj/skills
/plugin install ksef@ksefuj

What you can ask

Invoice for a client in Germany
Prepare an invoice for Müller GmbH in Berlin (EU VAT number: DE123456789) for a logo design project: 1200 EUR net, reverse charge. Date of sale 15 October 2026, payment by bank transfer within 14 days. My details are on the previous invoice I've attached.
Wrong buyer NIP
On my invoice from 3 October 2026 I entered the wrong NIP for my client: I swapped the last two digits. The invoice already has a KSeF number. How do I fix it?

What happens to your data?

The skills are only instructions and reference texts: they store nothing and send nothing anywhere. Invoice details you give your assistant are processed by its provider under the provider's own terms. They never reach ksefuj.to.

Check before you send

AI can make mistakes, and you're responsible for the invoice. Before you send the file to KSeF, run it through the validator and review the amounts and the buyer's details.

Open the validator

Frequently asked questions

Does it cost anything?
No. Both skills are free and all the code is public on GitHub. You use them in your own AI assistant, under its provider's terms.
Do I need to know XML?
No. You describe the invoice in plain words or attach a PDF, and your AI assistant prepares the XML file. Our validator then checks the result and shows you what to fix.
Will the assistant send the invoice to KSeF for me?
No. You get an XML file and send it to KSeF yourself, for example through the KSeF Taxpayer App (Aplikacja Podatnika KSeF).
Will it work in my AI assistant?
Yes, if your assistant supports skills in the open Agent Skills format (SKILL.md files). Claude (Claude.ai, the desktop app and Claude Code), OpenAI Codex and GitHub Copilot all do, among others. If you use a different assistant, such as ChatGPT, check its help pages to see whether it supports skills.

Claude, Codex and GitHub Copilot belong to their respective owners (Anthropic, OpenAI and GitHub). ksefuj.to is not affiliated with any of these companies.