A method for operating an internal combustion engine of a motor vehicle is provided, wherein at least one SCR catalytic converter for the after-treatment of exhaust gases of the internal combustion engine is present. The method serves to assure that a sufficient quantity of reducing agent is supplied for the operation of the SCR catalytic converter. The motor vehicle has a fuel tank (10) with a fill level sensor A (11) and a reducing agent tank (12) with a fill level sensor B (13). Signals from the fill level sensor B (13) or signals from the fill level sensor A (11) and the fill level sensor B (13) are acquired and evaluated by a navigation unit (16).