If you used car finance to buy a vehicle any time in the last 18 years, you could be in line for compensation.

It follows a recent court ruling on hidden commissions made by lenders to dealers, which opens the door for potential payouts to millions, if they are found to have been mis-sold finance.

If you are eligible, you are still in for a bit of a wait, and for now the advice is not to sign up with a claims company promising to help you get redress, because it won't speed things up and they will charge a fee.

But there are a few other things to bear in mind, if you are trying to work out whether you are likely to get compensation.

Most car buyers use motor finance where they borrow money and pay in instalments over time. In some cases, drivers pay monthly fees before paying a so-called "balloon payment" at the end.

Car dealers almost always receive a payment for their part in arranging the loan - a commission.

But a Supreme Court ruling on Friday has established that some dealers charged too much, or didn't explain the charges well enough to customers, and that those buyers should be compensated.

The key is whether customers were treated "fairly" although the regulator, the Financial Conduct Authority, is still working on exactly what that will mean.

One specific group of buyers who are likely to be eligible are people who took out car loans that included discretionary commission arrangements (DCAs). They were banned in 2021 but prior to that lenders gave car dealers leeway to charge higher interest and earn a percentage of that as commission.

If you still have your contract you can check the terms and conditions.

The Supreme Court ruled in a test case that Marcus Johnson should be entitled to compensation, setting one reference point for future cases.

Mr Johnson told the court he was presented with "an enormous amount of paperwork". He didn't read it all and signed, trusting the sales representative to talk him through the deal.

But 55% of what he was paying for the car was commission.

Anyone paying commission at that level is likely to be eligible for compensation, but it remains to seen how much lower rates would have to be, to count as fair, ruling a customer out of the right to compensation.

The FCA is setting up a compensation scheme. In October it will launch a six week consultation over how it should work, with the first payments expected to come in 2026.

So you can just wait until the scheme is available.

Alternatively, the charity Consumer Voice suggests writing now to your lender to establish the facts of your own case.

Lenders must acknowledge your complaint within eight weeks, and by submitting a complaint at this stage you may get an indication of how likely you are to receive any redress, says co-founder Alex Neill.

If you cannot remember the name of the lender involved the car dealership should be able to help you.

Consumer groups and the FCA advise against signing up with a claims company. Many are advertising their services online, but they cannot proceed with a claim until the FCA scheme has been set up and if they do manage your case they will take a cut of any compensation.

It is not clear yet how much individual customers will be entitled to as compensation, although it is likely to be related to how much they were charged.

A lot will likely depend on individual deals, including the type of car purchased.

Most claims are likely to be under £950, according to the FCA, including around 3% in annual interest.

Of course anyone who has taken out several car finance deals in the last couple of decades could be entitled to more than one payout.