Almost one million ‘forgotten’ households are now entitled to apply for help towards their energy bills this winter.
The Government committed to giving all households £400 towards the spiralling cost of gas and electricity last year.
Most people who deal with their energy provider directly have been receiving the rebate automatically via a monthly reduction from their direct debit since October.
Others who use top-up meters are being sent vouchers.
However, around 900,000 people who live in holiday parks, houseboats, off-grid or in care homes have been unable to apply for the rebate so far this winter.
An online portal to apply for the Energy Bills Support Scheme Alternative Funding is now open.
Those who wish to apply are being advised they will need to supply an email address, phone number and bank account details.
Those not registered for council tax will need to provide proof of address via a bank statement or tenancy agreement.
For those living in a care home, the government is also asking for an invoice for fees from the past three months and a statement from the care home including the applicant’s name and address and funding agreement.
It is believed the £400 rebate will arrive in one lump sum and could take up to six weeks to arrive.

According to the BBC, once an application is submitted information will be passed to local authorities and a home visit could be required.
The move comes after criticism from the thousands of households that have been unable to claim any help despite huge increases in energy costs.
Sue Marshall who lives in a park home in Nottinghamshire told the BBC: “I feel as if we have been forgotten.
“Nothing at all has come to fruition.”
The Government says that despite complaints about the operation of its Energy Bills Support Scheme (EBSS) more than three quarters of all vouchers have been redeemed and £1.7 million was used in January alone.
It means that a record amount of Government support reached some of the country’s most vulnerable households in January, with vouchers redeemed by those on traditional prepayment meters.
Some £530 million has been provided so far under the scheme, it revealed.
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However, the Government has condemned “disgusting” scam emails that are seeking to “rip off people” trying to access its support.
Scammers have attempted to target UK households by impersonating the Government through emails saying they are eligible for a £400 discount.
The emails ask the recipient to share details including their name, address and debit or credit card details in order to “receive the rebate”.
The Government said it does not currently have data on the total volume of scams in this area, but it is trying to track down scammers and counteract them.
It added that cybercriminals are “opportunistic” and will use issues such as rising energy bills to try to trick people into sharing their financial or personal details.
People who think they have received suspect emails can forward them to [email protected] and to Action Fraud.