Why is there a six-digit occupation code (KZiS) in the contract?
KZiS is the official classification of ~2500 occupations; the six-digit code goes into the oświadczenie, the contract and reports. The authority compares the code and pay from the oświadczenie with the contract: the contract pay may not be lower than in the oświadczenie; higher is fine.
Finalise the terms in step 01, not at contract signing. But not every change is a new legalisation procedure: a pay raise (same duties and working time) does NOT require a new oświadczenie or notification to the authority — because the oświadczenie states the lowest wage, not the exact amount. A change in pay still requires an annex to the employment contract (labour law — a separate obligation, not to be confused with legalisation). A new legalisation procedure is required by: change of employer, a material change of duties/position, a drop below the oświadczenie threshold.
Legal basis — verify at the source
Legal state: 07/2026. This is general information, not legal advice — check the wording in the source linked above before you act.