Overview
KSeF (Krajowy System e-Faktur) is Poland's national e-invoicing system, and the obligation to issue structured invoices applies to active VAT taxpayers in a phased way: when a company must switch depends on its size under the schedule published by the Ministry of Finance. The rollout has been postponed more than once, so confirm the date that applies to you against the current official schedule before acting. What does not change is the technical requirement — once your obligation applies, B2B invoices must be issued as structured FA(3) XML with a KSeF number and a UPO.
Who is covered
KSeF is operated by the Ministry of Finance (Ministerstwo Finansów). The obligation targets taxpayers with an active Polish VAT status that document B2B transactions with invoices. Foreign entities without a Polish NIP are generally not obliged themselves, but they may still need to issue a structured invoice for a Polish transaction, so this is not a topic to resolve by assumption.
Phasing by company size
The Ministry of Finance has announced the obligation in stages, with the largest taxpayers first and the smallest last. Because the schedule has shifted over time, this article deliberately avoids repeating fixed dates as if they were current law — a date that was true a year ago may no longer apply to you today. Treat the official schedule on podatki.gov.pl as the single source of truth for your company's deadline.
How to confirm your date
Confirm three things: that your entity is an active VAT taxpayer, the size category you fall into, and the date the Ministry currently sets for that category. If you are a SaaS or e-commerce seller with a Polish NIP, your accountant can confirm the category in minutes. Do not rely on a competitor's landing page or an old article for a date that triggers a legal obligation.
What it means for your integration
Whatever your date, the technical path is the same: generate a valid FA(3) XML, authenticate to KSeF, send the encrypted document and store the KSeF number and UPO it returns. An API such as Notaly's turns a JSON payload into that pipeline, so the deadline becomes a configuration change rather than a new engineering project.
FAQ
Who is covered by KSeF? Active Polish VAT taxpayers issuing B2B invoices, under the schedule set by the Ministry of Finance. Confirm your own date against the current official schedule.
Does KSeF apply to B2C invoices? KSeF is essentially a B2B system. Electronic invoicing to consumers generally depends on separate consent rules, so confirm your case with an accountant.
Disclaimer
Notaly is not a tax, accounting or legal advisor. This article is general information, not tax advice, and may be outdated. You are responsible for your own VAT compliance; confirm with a qualified accountant where required.
Sources
Source: www.podatki.gov.pl