Lenders including HSBC, Lloyds and Santander could be on the hook for as much as £18 billion in consumer compensation over car finance misselling, the U.K.’s Financial Conduct Authority said Sunday.

The FCA confirmed it would consult on a market-wide compensation facility after a landmark court case at the U.K.’s highest court wrapped up on Friday. The regulator said it anticipated the bill could be between £9 billion and £18 billion for motor finance lenders, but estimated costs would land somewhere in the middle — significantly lower than previous forecasts of £44 billion.

Most of the affected consumers will probably receive less than £950 each, the FCA said.

Although the Supreme Court mostly sided with banks in the historic ruling Friday, which looked at whether consumers had been missold car finance after banks paid motor brokers large commissions, judges upheld the appeal of one consumer due to the size of the commission the bank paid to the motor dealer and how it was disclosed.

“Where consumers have lost out, they should be appropriately compensated in an orderly, consistent and efficient way,” the regulator said in a statement.

The FCA will consult properly in October, but today set out the parameters of what a compensation scheme could look like. The facility would cover both discretionary and non discretionary commission arrangements, and the methodology would be informed by degree of harm.

It will consider what interest needs to be paid on awards, whether they should date back to as far as 2007, and whether customers should have to opt in or opt out of any arrangement.

If the compensation scheme goes ahead, the first payments should be made in 2026, the FCA said.

Fiona Maxwell contributed to this report.