Written with people moving from Turkey in mind. The Portuguese rules still apply more broadly.
Overtime Pay Rights
In Portugal, overtime (Trabalho Suplementar) is strictly regulated. The first hour of overtime must be paid at regular rate +25%, and subsequent hours at +37.5%. Work on rest days (Sundays/Holidays) is paid at +50%.
Companies often try to offer "Time in Lieu" (extra vacation days) instead of cash. You have the right to refuse this if it wasn't agreed upon in your contract. Unpaid overtime is illegal.