Ratepayers across the state have been slugged millions of dollars in extra rates following a widespread property valuation blunder.

Eleven councils have overcharged ratepayers well over $4 million in total, due to an administrative error, the Essential Services Commission has found.

The total cost is still unknown, but the error means thousands of ratepayers across Victoria will receive anything from small change to a sizeable refund.

Ratepayers across the state have been slugged millions of dollars in extra rates following a widespread property valuation blunder. Credit:Jessica Shapiro

It's understood the bungle occurred after councils relied on preliminary property value data provided by the Victorian Valuer-General, rather than final, certified data.