Robin Hood Energy, Toto Energy, Gnergy, and Delta Gas and Power could lose their licences if the payments are not made by the end of October.
Four energy suppliers have been given a month to pay £14.7 million owed in green taxes or face losing their licences, energy regulator Ofgem has announced.
Robin Hood Energy, Toto Energy, Gnergy, and Delta Gas and Power failed to meet the original deadline of September 1 for renewable energy payments, which all suppliers must make.
Failure to make the payments is seen as a warning sign in the industry that a company may be struggling.
Of the three that failed to meet the second deadline last year, one – URE Energy – had its licence removed and the other two – Economy Energy and Spark – went bust.
The payments buy Renewable Obligation Certificates which show to Ofgem that the companies are funding green initiatives to help move the UK away from relying on fossil fuels.
Robin Hood Energy, which is a not-for-profit supplier owned by Nottingham City Council, owes £9.4 million, Toto Energy £4.6 million, Gnergy £673,876, and Delta £91,937.
Mary Starks, executive director of consumers and markets at Ofgem, said: “The Renewables Obligation schemes provide important support to renewable electricity generators and play an important role in Great Britain’s journey to a net zero-emission economy by 2050.
“Supplier failure to comply with the schemes undermines the integrity of the schemes and is unacceptable.
“It also adds to the costs of other suppliers who do meet their obligations as they have to absorb or make up any shortfall.
“This enforcement action sends a strong signal that suppliers must meet their obligations, or pay the consequences, which could mean losing their licence.”
Robin Hood has been struggling recently, and has seen the local authority that owns it call in external advisers to assess the business.
Nottingham City Council has invested around £40 million into the company, but it continues to struggle and annual accounts due with Companies House are now two months overdue.
Simon Neville is PA City Editor.