Step 2 of 4 · ProjectsBy jurisdiction

13 open source tax projects for Poland.

Every project on the list for Poland, grouped by kind. Global tools have a page of their own. Entries without a warning come first in each group; the labels mark what to check.

13 projects12 maintained7 on the map19 jurisdictions + globalFacts checked 6 Oct 2026

Browse these by tax area

Income tax Corporate tax Payroll tax VAT & indirect Cross-cutting

Calculators

2 projects

Small tools that compute one tax for one country.

ratioNuxt 4 calculator for Polish B2B contractors comparing tax forms, ZUS contributions and IP Box.CalculatorPLFor individual taxpayers

tax-interest-calculator (nieinter)Simple Python calculator for interest on late Polish tax payments.CalculatorPLInactive since 2025For individual taxpayersLicence unknown

APIs

6 projects

Validation, rates, filings and registries you can call directly.

KSeF official clients (C#, Java)Official C# and Java clients for KSeF, Poland's national e-invoice system, from the Ministry of Finance.APIPL

ksef-apiIntegration guide for KSeF 2.0, Poland's national e-invoicing system.APIPL

ksef-php-clientPHP client for KSeF, Poland's national e-invoicing API.APIPL

ksef4jJava client for Poland's KSeF 2.0 e-invoice API, with fluent builders and Spring Boot autoconfiguration.APIPL

ksefujValidator for Polish KSeF FA(3) e-invoices: XSD, business rules and tax maths, as web app, npm and CLI.APIPL

NIP24 PHP clientPHP client for NIP24: validates Polish NIP, REGON and KRS numbers and EU VAT IDs.APIPL · EUNeeds a paid service

Automations

4 projects

Reusable workflows for provisions, reconciliations and compliance runs.

KSeF PDF generatorOfficial TypeScript generator of the PDF visualisation of a KSeF e-invoice.AutomationPL

Accounting AI AgentAI accounting agent for Polish small businesses: bookkeeping, KSeF e-invoices and a tax calendar.AutomationPLNeeds a paid service

medusa-infaktMedusa v2 plugin that issues Polish invoices through inFakt and files B2B invoices to KSeF.AutomationPLNeeds a paid service

pillar2-demo (Poland)Streamlit MVP that fills Poland's GLB-Z2 and GIR-1 forms, validates the XML against the XSD and saves it.AutomationPLDemoLicence unknown

Tax datasets

1 project

Rates, treaties and statistics, open and versioned.

myTransferPricing referenceSummaries of 18 OECD transfer pricing country profiles, with a prompt that reviews a Local File against one.Tax datasetAT · BE · BR · DK · FR · DE · GR · IE · IT · LU · NL · PL · SG · ES · SE · CH · UK · US

Labels mark what to check before you rely on an entry: inactive or archived code, demos, paid services and unclear licences. Only maintained projects for companies and tax authorities appear on the map. Search and filter the whole list.

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Next · Step 3 of 4The gapsThe activities with no open project yet, and the partly covered ones, with what to build on.