If you require certification of the meter, you will have to send it to a PMEL facility. They have the standards of weights and measurements.
Meters are very sturdy equipment, some places are required to have the unit calibrated once a year. I have my units calibrated once a year which includes my power supplies, meter and scope.
You could also use a zener diode that is set to a specific voltage to test your unit. Many ways to test if you think about it.