Victoria police is in the process of contacting all Victorian firearm license holders who may have been overcharged or undercharged license fees.
It was discovered Victoria Police had been incorrectly charging fees dating back to 1997.
Some license holders will be eligible for refunds, and no action will be taken against those who were undercharged.
Only license holders who hold a category A or A/B license at the same time as a category C will be affected.