This paper presents the characterization of a resistive HVDC reference divider and methods to establish a traceability. The divider is designed for use as a laboratory reference for calibration of HVDC measuring systems up to 1000 kV. Targeting a measurement uncertainty of 20 ppm at full voltage has put a focus on the temperature coefficients of the resistors, elimination of humidity dependence and control of leakage currents in the high voltage arm.