The regulator is following up the review with individual offenders, while it also expects others firms to take action.
The FCA said customers could struggle to tell the difference between paying upfront or in instalments, while in many cases people might not realise that there is a price difference between the two.
Linda Woodall, acting director of supervision at the FCA, said: “Consumers should expect clear information about the payment options available to them.
“Regardless of whether people choose to pay upfront or in instalments, it’s important that they can see exactly what they are signing up for and how much it costs so they can decide whether they are getting a fair deal.”
The review included 13 insurers and 30 insurance intermediaries, including four price comparison websites.
Some firms acting as credit brokers failed to disclose the name of the provider, while in some cases it was not made clear that a fee would be charged at all.
If a firm is providing regulated credit or is acting as a credit broker they must provide a representative example of the interest rate, any fees or charges and a representative annual percentage rate (APR) and the total amount payable.