There is a complaint committee operated by the Consumers Association and the Icelandic Tourism federation (SAF). The committee however only accepts cases concerning companies that are members of SAF. Most of the largest car rentals in Iceland are members and therefore it is possible to refer disputes to the committee regarding those companies. It may therefore be a great benefit for consumers to do business with a car rental that is a member of SAF.
If you live in Europe and have a problem regarding an Icelandic car Rental Company, you can contact the ECC centre in your home country. They will then forward your complaint to the ECC centre in Iceland and both centres will then work together to resolve the issue.