The energy regulator Ofgem told BBC's Money Box that it is writing to chief executives demanding to know how many people have been sent "back bills". Back billing is when customers receive new bills for energy used longer than 12 months before - a practice that was banned seven years ago.

The energy regulator is gearing up to introduce a series of major changes that could see you shelling out more or less on your bills, depending on your energy consumption

OFGEM has required energy suppliers to offer tariffs with low or no standing charges, allowing customers to pay costs as part of the unit rate. This change aims to give consumers more flexibility and potentially lower their energy bills.

A report by consumer watchdog Citizens Advice claimed that network operators made use of a regulatory loophole set by Ofgem

The energy regulator said it is consulting on bringing in the option under the price cap that would cover so-called zero standing charge tariffs

Energy regulator Ofgem has issued a major update on plans to introduce new energy tariffs with no standing charges. Standing charges are a daily charge paid by all households, which cover the fixed costs of delivering energy to homes and businesses. Currently, the energy price cap dictates the maximum amount energy suppliers can charge.

Standing charges are set by energy suppliers and rack up daily, regardless of how much energy you use that day.