Sending FA(3) invoices
Invoices generated by your system, validated against the official schema before they leave.
For companies that invoice in Poland
KSeF in your own system, next to the accounting app
Your invoices come out of your own system: an OMS, a CRM, a SaaS, maybe one built with AI. Since 2026 they have to go through KSeF. I add sending and receiving to it, test it on the KSeF test environment first, and keep it working when the schema or the API changes.
- “someone you can always count on”public LinkedIn recommendation
- “a true bias for action”client CTO, on LinkedIn
- 15+ yearsshipping software
- Free call, no pitch deck30 minutes, then you decide
What the integration covers
UPO and KSeF numbers
Confirmations collected and stored next to each invoice in your system.
Receiving invoices
Purchase invoices fetched from KSeF into your system, if you want them there.
Corrections and offline mode
Corrective invoices and the offline procedures, so a KSeF outage does not stop sales.
How it works
A short call
Which system issues invoices, which invoice types, how many a month.
One to three weeks
The integration, tested on the KSeF test environment with test data.
Production
Switching to production with your certificate or token, on your accounts.
SLA
Optional monthly care for schema and API changes, which the Ministry announces in its changelog.
Systems I can connect
- Your own OMS, CRM or SaaS, including apps built with AI.
- Older desktop systems with a database or an API to read invoices from.
- Systems of foreign companies that sell in Poland, documented in English.
Proof
I build and run integrations that move money and documents between systems, and I test them before they touch production. Try the free KSeF invoice validator on one of your invoices.
Back-office task management: team lead of four, no product manager
- The problem
- A back-office tool needed new features, a UI refresh and a faster pipeline, with no product manager in sight.
- What I did
- I led four engineers and kept coding. Trunk-based development with CI/CD, live updates over server-sent events, a stopped parallel initiative that analysis showed would not pay off, priorities set directly with department managers.
- Result
- “Measurable changes in some key metrics” and “a true bias for action”, in the client CTO’s public LinkedIn recommendation.
See also: Full-stack & custom software
Four side projects on Cloudflare Workers under one domain
- The problem
- Ideas die when deploying them costs a weekend. I wanted a path from idea to a URL in an evening.
- What I did
- Korpo Tłumacz, Wyrocznia, Migawki and Przemo (Agent): each a Worker with static assets, Workers AI with per-IP and global rate limits, a cost cap in a Durable Object, R2 for generated images, a first-party PostHog proxy and a CSP without inline scripts.
- Result
- Live at ciunkos.com/korpo-tlumacz, /wyrocznia, /migawki and /przemo. This page runs on the same pattern.
See also: Cloudflare · AI & agents
An AI coding agent as a team member, under enforced rules
- The problem
- Coding agents produce ten times the output and ten times the mess. A team of four wanted the speed without a slop swamp on main.
- What I did
- I authored the rule set shared by Claude Code and Codex: mechanical checks over written rules, lint and test gates for security, API surface and CSP, agents working on main with hooks, every PR reviewed by a human, AI-assisted content disclosed as such.
- Result
- In 2026 the agent opened about 30% of merged pull requests across two products and I reviewed about 85% of them. My own output went from under 1,000 to 5,000+ commits a year.
See also: AI & agents · Full-stack & custom software
KSeF in your own system, next to the accounting app
Sending and receiving invoices through Poland’s KSeF from your own system, OMS, CRM or SaaS: sessions, FA(3) invoices, UPO, corrections and offline mode, tested on the KSeF test environment, with an SLA for schema and API changes.
FAQ
Questions
From when is KSeF mandatory?
According to the Ministry of Finance, from 1 February 2026 for companies with 2024 sales above PLN 200 million, and from 1 April 2026 for everyone else.
Our accounting app already supports KSeF. Do we need this?
Only if invoices are issued outside it, in your own system. Then that system needs to send them, or hand them to the accounting app reliably.
Do you need access to our production?
Not at first. Everything is built and tested on the KSeF test environment with test data.
How long does it take?
Usually one to three weeks, depending on the system and the invoice types.
Let’s find out in 30 minutes
A free 30-minute call. You bring the problem, I bring questions. No prices on this page because scope comes first.
If I am the wrong person I will say so on the call and point you to someone better.
or write to ciunkos@gmail.com
After you book: a calendar invite, then the call. Nothing else to fill in.
Available from November 2026 · B2B contract or employment · Wrocław, Poland (CET), remote