Dynamic currency conversion at the card terminal
Nationwide, worst in tourist areas and at airportsVery commonThe card machine or ATM screen asks whether you want to pay in your home currency instead of złoty, sometimes showing the home-currency option as the large green button. Accepting hands the exchange rate to the machine's operator.
How to avoid it: Always choose to be charged in PLN. Your own bank will convert at a better rate. This is legal, so no one will refund it.