Latest Ofgem data shows dozens of energy suppliers were behind with payments to the renewable obligation buyout fund for the year to April 2019.
Some 42 suppliers were late in paying into the buyout fund, creating a £206m shortfall.
Failure to set aside RO levies has contributed to a spate of supplier exits over the last two years, with Toto the latest to go bust owing millions and others likely to follow.
Despite eventually taking action to tighten up market entry requirements, Ofgem suggests between one and four suppliers are expected fail per year, which would represent a significant slowdown on current rates.
The regulator last month also outlined plans to check the finances of existing supply companies.