Bulb Energy (Bulb) owed £254m to customers who had paid for their electricity and gas in advance ahead of its collapse, according to documents set out by administrators Teneo.
The news was first reported in The Financial Times, and follows the publication of joint administration proposals from Interpath Advisory, the administrators overseeing parent company Simple Energy.
City A.M understands that Bulb could be sold jointly or potentially in pieces, with an offload targeted for this spring.
The UK’s seventh biggest energy firm fell into special administration in November.
The energy firm has since been propped up £1.7bn in public money, with the supplier’s 1.7m customers supported through the winter.
This was the biggest public bailout since the collapse of the Royal Bank of Scotland at the height of the financial crisis in 2008.
Customers whose accounts were in credit will not lose out from Bulb’s inability to pay back costs.
However, The Financial Times suggests the price of honouring the balances could ultimately be met by taxpayers or energy bill payers under the funding deal struck with the UK government.
It also revealed Bulb had £640m of overall liabilities, which could explain its inability to find a buyer over recent months.