Why do you never receive the full amount you negotiated during the job interview? Once your monthly gross 1 is defined, the law mandates the deduction of certain percentages from that pool before you receive the payment. These items primarily go into public coffers (funds and budget).
The most solid deduction and the largest hit to the gross salary in absolute terms is intended for your days when you will no longer be able to work. It is paid to the competent pension fund (PIO/MIO fond). Pension contributions usually represent a significant percentage of your Gross 1 amount.
Tax on your earnings that finances the administration (schools, infrastructure of your place of residence). This is a variable item — the rate depends on the level of your income and legally determined local reliefs.
Many municipalities and cities may charge additional taxes or add their own rates to the state income tax. This directly depends solely on the city in which you reside.
In addition to legally mandatory pension payments and taxes, your net salary may be burdened by specific withholdings that are realized during payment (effectively deductions from your Net amount):