Work without a contract (employment or civil law) is illegal. It means a lack of compulsory social security insurance for the employee, non-payment of taxes, etc.
In general, the employer is responsible for signing the contract. If they deceived you about signing a contract or paying taxes, they are responsible for it. The employer is obliged to draw up the contract in two copies and give you one of them.
However, if you deliberately choose to work under the table, you may be punished. That is the case when you:
-don’t have a valid visa or other document entitling to stay in Poland
-don’t have a work permit, and you are not exempt from it (like the citizens of Ukraine currently),
– or the basis for your stay excludes work (e.g. you have a tourist visa).
For illegal work, you can be punished by: a fine of PLN 20 to PLN 5,000 (art. 120 Law 2 of the Act on foreigners), obligation to return (leave Poland), and be prohibited from re-entering the territory of the Republic of Poland and other Schengen countries – for a period from 1 year to 3 years (art. 318 and art. 319 point 2 of the Act on foreigners).
If you register with the Employment Office as unemployed and then take up a job without informing the Office, you may receive a fine of between PLN 500 and PLN 5000.