Back-billing for energy use after more than four months will not be allowed in Victoria from next year.

A ruling from Victoria’s energy regulator has capped the time for retailers to properly bill customers, tightening it from nine months to four.

Essential Services Commission chief executive John Hamill said the new rule means Victorians can’t get slugged with more than four months of back bills if their retailer makes a mistake.

The ruling will come into effect in 2021 and will come with additional safeguards for Victorians, such as a limit on how much retailers can charge for missed payments.

Increases to energy contracts within a year have also been banned from July 1.