KSEF-006:Unit code not recognized
Unit of measure must be from Polish classification. Common codes include szt. (piece), kg, m, l, usł. (service).
Engine Classification
Business data required · Explicit input workflow · No assumptions made
Required input: Unit of Measure
What is KSEF-006?
KSEF-006 is a fatal validation rule defined in the KSeF specification (POL national rules). It checks whether unit code not recognized.
When this rule fires, the invoice is non-compliant and will be rejected by Peppol access points and national validation services. The sending system receives a rejection response and the invoice does not reach the buyer.
Why This Error Matters
KSEF-006 is a hard failure. Invoices that trigger this rule are rejected at the access point and never reach the recipient. In Peppol networks, this means your sending system receives an MLR (Message Level Response) with a rejection status. The invoice must be corrected and re-sent, adding delay to your payment cycle.
Validator Behavior
- ·Causes invoice rejection
- ·Error returned: KSEF-006
- ·Specification: KSeF
How to Fix It
Technical Reference
Code Example
<JednostkaMiary>szt.</JednostkaMiary>Common Causes
- ·Using English unit names
- ·International codes not mapped
- ·Invalid abbreviation
Seeing this in production? The API handles KSEF-006 automatically. See the fix response →
Frequently Asked Questions
Unit of measure must be from Polish classification. Common codes include szt. (piece), kg, m, l, usł. (service).
Use Polish unit codes from the official classification. You can also use Invoice Navigator's automatic Fixer tool to correct this instantly.
Yes, KSEF-006 is a critical error that will cause invoice rejection. It must be fixed before submission to ensure your invoice is accepted by the recipient's system.
Many instances of KSEF-006 can be automatically corrected using Invoice Navigator's Fixer tool. Upload your invoice and the tool will identify and fix common issues, including unit code not recognized.
Last updated: 19 January 2026
Handle KSEF-006 Automatically in Your Pipeline
The compliance engine auto-remediates this error with controlled safety policies and evidence pack generation.