Knowledge Base
How to invoice in Poland by the book, and what a tax month looks like in a micro-firm — a sole proprietorship or a spółka z o.o. Step by step, with the legal basis and with the boundaries the app does not cross.
Browse by Category
From the first invoice to closing the year — organised by topic
Getting Started
First steps: the account, your company data and the KSeF connection
2 articles
B2B accounting
Ryczałt, the health contribution, ZUS contributions, the annual JPK_EWP and IP Box — the month and the year of a sole proprietorship
5 articles
KSeF Integration
How KSeF works, statuses, environments, and troubleshooting
6 articles
Invoicing
Invoice workflow, statuses, and transmission process
3 articles
Invoicing in Poland
Polish invoicing rules, VAT rates, deadlines, and legal requirements
8 articles
AI & Automation
Connect AI assistants to your company over the MCP protocol
1 articles
Getting Started
First steps: the account, your company data and the KSeF connection
B2B accounting
Ryczałt, the health contribution, ZUS contributions, the annual JPK_EWP and IP Box — the month and the year of a sole proprietorship
Sole proprietorship on a B2B contract
From the invoice to closing the year: what a tax month looks like in a one-person firm.
Ryczałt 12% or 8.5% on a B2B contract
Where the ryczałt rate comes from, why borderline work stays unsettled, and how the rate works in the app.
The health contribution on ryczałt in 2026
Three brackets instead of a percentage: what comes off revenue first, and what still lands on you.
The annual JPK_EWP: who files it and when
How JPK_EWP differs from JPK_V7, what goes into the file, and why you start the submission yourself.
IP Box at 5%: conditions, register, bill status
What the 5% rate really covers, why ryczałt rules it out, and where the UD116 bill stands.
KSeF Integration
How KSeF works, statuses, environments, and troubleshooting
What is KSeF?
Introduction to the Polish National e-Invoice System
KSeF Statuses
Understanding invoice statuses in KSeF
Connecting to KSeF
The two ways to authenticate, and what Biurko does with your credentials
Sending Invoices to KSeF
How to submit invoices to the National e-Invoice System
KSeF Environments
Production, Test, and Demo environments explained
KSeF error codes
What a rejection code means and what to do about it
Invoicing
Invoice workflow, statuses, and transmission process
Invoicing in Poland
Polish invoicing rules, VAT rates, deadlines, and legal requirements
Types of Invoices
VAT invoice, proforma, advance payment, corrective, margin and simplified invoices
Required Invoice Elements
Mandatory fields on a Polish VAT invoice per Article 106e of the VAT Act
VAT Rates in Poland
Standard, reduced, zero rates and VAT exemptions explained
Invoice Deadlines
When to issue invoices — the 15th-day rule, exceptions, and consequences
Corrective Invoices
When and how to issue correction invoices and correction notes
Split Payment (MPP)
When split payment is mandatory and how it works
Foreign Currency Invoices
Currency conversion rules, NBP exchange rates, and EUR invoicing
Archiving Requirements
Storage periods, digital archiving rules, and KSeF as an archive
AI & Automation
Connect AI assistants to your company over the MCP protocol