Energy firms in the UK will be writing to customers over the next few days to warn them of energy bill rises in April.
According to Citizens Advice, energy suppliers must provide their customers with "reasonable notice" of price rises or changes which will leave them worse off.
With the Government's current plan of upping its Energy Price Guarantee (EPG) to £3,000 from £2,500 next month, customers will need to be told about the changes as soon as possible.
Energy UK, which represents suppliers, told the BBC suppliers would be writing to customers to let them know how much their bills were going up on average by £500 within the "next few days".
The Government is being urged to axe the planned £500 rise of the Energy Price Guarantee rise in April over fears it will increase the number of people already struggling to pay.
MoneySavingExpert founder Martin Lewis recently wrote a letter to the Chancellor urging for a pause on the 20% increase as it could be even more damaging amidst the current cost of living crisis.
The consumer rights campaigner said the £500 rise could force nearly two million households into fuel poverty increasing the overall number to around 8.4million.
He also noted that the pause should be implemented before the Spring Statment on March 15 as energy firms needed to know and inform their customers beforehand.
Recently, Energy Secretary Grant Shapps said he was "very sympathetic" to the idea of a halt to the rise and said he was "working hard" with the Chancellor on the issue.
He told the Times newspaper: "I completely recognise the argument over keeping that price guarantee in place, and the chancellor and I are working very hard on it.
"I'm very sympathetic to making sure that we protect [people]. We're looking at this very, very carefully.
The MoneySavingExpert, alongside many others, called on the Government to halt the rise until July as a number of experts expect energy bills to fall below £2,500 by then.
This would mean the Government would only have to provide energy support at the current levels until then.
Energy UK has also urged the Government to hold the level of support at £2,500 until then.
Campaigners will be watching closely to see if the Chancellor makes an announcement during the Spring Budget this month.
