When a (sub)contractor has tax debts or social debts, there is an obligation to withhold from the invoice in certain sectors, including the building sector. A certain percentage of the invoice amount must then be withheld and transferred to the National Social Security Office (RSZ) (in case of social debts) or the FPS Finance (in case of tax debts). As a client you must therefore verify whether your contractor has any debts or not.

In case of social debts you must transfer 35% of the invoice amount. In case of financial debts you must transfer 15% of the invoice amount.

You can find more information here.