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Poland · Agentic SaaS development

SaaS Development for Companies Selling in Poland

KSeF, Poland's national e-invoicing system, has been mandatory since 1 February 2026 for businesses whose 2024 sales exceeded PLN 200 million and since 1 April 2026 for all other businesses. Until 31 December 2026, invoices totalling no more than PLN 10,000 a month, VAT included, may still be issued outside it. For a SaaS company billing Polish businesses, invoicing stops being a PDF template and becomes structured XML sent through an API.

We are Curiosive, a software studio in Ankara, Türkiye, and we build with AI coding agents under senior engineer review. Agents produce the CRUD screens, admin views, migrations and test suites. Engineers design the multi-tenant data model, tenant isolation, plan and entitlement logic and the billing webhooks, because those are the parts that leak one customer's data to another or charge someone twice when they go wrong.

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KSeF e-invoicing in SaaS billing for Poland

Since 1 February 2026, a KSeF e-invoice has been an XML file in the FA(3) logical structure, and finance and accounting software connects to KSeF through the KSeF 2.0 API. Invoices with attachments can only be issued from commercial software integrated with that API, and KSeF archives each invoice for 10 years. Receiving invoices through KSeF has been obligatory since the same date, and the Ministry of Finance FAQ updated 11 September 2026 says that from 1 January 2027 the KSeF invoice number must be included in the payment title when an invoice is paid. Two scope rules shape the design: B2C invoices to consumers are voluntary in KSeF, and a foreign company registered for Polish VAT is not obliged to use it if it has no seat or fixed establishment in Poland, or if that establishment takes no part in the supply.

VAT and złoty pricing for SaaS customers in Poland

Poland's standard VAT rate is 23%, with reduced rates of 5% and 8% and no super-reduced or parking rate, per the Your Europe rate table last checked 13 July 2026. The currency is the złoty (PLN), not the euro, so if plans are priced in złoty, currency belongs on the plan record rather than being assumed in code. Under EU VAT rules, a business customer in another EU country usually pays VAT at its own country's rate through the reverse charge, though with several important exceptions. Telecommunications, broadcasting and electronic services sold to consumers are taxed in the customer's country, though below a threshold of EUR 10,000 they may be taxed where the seller is established, and the One Stop Shop lets a seller declare that VAT through one EU country. It is worth confirming your position with an accountant.

BLIK and strong customer authentication for Polish subscribers

BLIK users completed 1.6 billion transactions in the first half of 2026, and a BLIK press release of 25 September 2026 says Stripe customers in over 30 countries can now offer BLIK automatically, so it belongs in checkout testing for Polish buyers. Card payments carry the PSD2 rules on strong customer authentication, applied since 14 September 2019: a provider may skip authentication for a remote electronic payment of no more than EUR 30, but only while the payer's remote payments since the last authentication stay within a cumulative EUR 100 or five consecutive transactions. The European Parliament's Legislative Train listed the Payment Services Regulation and PSD3 as close to adoption on 20 September 2026, so these rules may still change. Billing webhook handlers are written to be idempotent, so a redelivered event never activates or cancels a plan twice.

UODO, data protection and Data Act exit terms in Poland

When a Polish company puts personal data into a SaaS product, its GDPR supervisory authority is the Urząd Ochrony Danych Osobowych (UODO), and the national law supplementing the GDPR is the act of 10 May 2018 (Dz.U. 2018 poz. 1000). The EU Data Act, applied since 12 September 2025, places data processing services in the IaaS, PaaS and SaaS delivery models in its recitals. Switching terms must be set out in a written contract, with a notice period of no more than two months and a transitional period of no more than 30 calendar days. Until 12 January 2027 only reduced switching charges are allowed, capped at the costs directly linked to the switch, and from that date none at all. A complete, documented export for each tenant is easier to design in than to retrofit.

Multi-tenant SaaS: what agents build and what engineers own

Tenant separation sits at the foundation of the data model, so engineers design it first and review every query that touches it. The same goes for the parts specific to selling in Poland: the KSeF connector, plan records carrying złoty prices and VAT evidence, and the webhooks that turn a BLIK or card payment into an active subscription. Agents produce the volume around those boundaries, each change a diff that a senior engineer reads before it merges. Our SaaS work includes Reveal Software (reveal.software), personal video onboarding for SaaS products, for a client in Romania; PicKey (pickey.ai), a visual password manager with subscription billing, for a client in India; and Inspire Film (inspire.film), a virtual cinema with per-title entitlement, for a client in Spain. Polish clocks run one or two hours behind Ankara's, depending on the season.

Proof

Published project examples

Reveal Software

Reveal Software

Release Coach AI

Release Coach AI

Inspire Film

Inspire Film

Poppin

Poppin

Zing Coach

Zing Coach

ChurchBee

ChurchBee

AI-accelerated development
from$2,000
per month

Senior engineers building your product with AI coding agents: web, mobile, SaaS or browser extension, reviewed before anything ships.

  • Web, mobile, SaaS and browser extensions
  • AI-assisted delivery under senior engineer review
  • Scope and capacity agreed in writing, renews monthly

AI-accelerated development, billed monthly. We confirm scope, capacity and start date in writing before checkout.

Questions

The things people ask before starting.

Do SaaS companies in Poland have to issue invoices through KSeF?

Most do for business invoices. KSeF became mandatory on 1 February 2026 for businesses with 2024 sales above PLN 200 million and on 1 April 2026 for the rest, with up to PLN 10,000 a month, VAT included, still allowed outside it until 31 December 2026. Issuing B2C invoices to consumers in KSeF is voluntary.

When do KSeF penalties start in Poland?

Not before the end of 2026: current law defers penalties for KSeF errors until then. On 16 September 2026 the Ministry of Finance announced an extension to 31 December 2027, which needs a statutory amendment it has only started drafting. The obligation to use KSeF is not postponed and reaches the smallest businesses on 1 January 2027.

Can a SaaS product sold in Poland accept BLIK payments?

Yes, through a payment provider that offers it. BLIK's press release of 25 September 2026 says Stripe customers in over 30 countries can now offer it automatically, and the system had 21.6 million active users at the end of June 2026.

What does it cost to build a SaaS product for the Polish market?

Our one offer is AI-accelerated development from $2,000 per month, with scope and capacity agreed in writing after a discovery call. Work specific to Poland, such as a KSeF integration, złoty pricing or a Data Act export path, adds scope, which the discovery phase turns into a plan and an estimate.

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How it starts

What happens after you write to us.

  1. 01

    You describe the product

    One paragraph on what you are building, roughly when you need it, and who it is for. No brief, no form with fifteen fields.

  2. 02

    You get a reply within a day

    From the engineer who would do the work, not a sales team. If we are not the right fit we say so, and where possible we point you somewhere better.

  3. 03

    You get a scoped plan

    Scope, price and timeline in writing before anything is committed. You decide with the numbers in front of you.

No long contract to begin, no lock-in to our tooling, and the code is yours from the first commit.

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