Over half of tenants living in rent pressure zones don't realise there are restrictions on their landlords.
A new report by the RTB found that rent in rent pressure zones would be up to 3 per cent higher if the measures hadn't been brought in.
Under the legislation, landlords can't increase rent by more than 4 per cent a year.
Director of the Residential Tenancies Board, Rosalind Carroll (pictured), says tenants don't realise that the rule also applies to new tenancies.
"Rent pressure zones and the cap on rents in terms of that four per cent increase applies not only to existing tenancies, but to a tenanciy that is being re-let in the market," she said.
"Lots of people get that it applies within your existing tenancy, but the research found that a lot of people didn't get it at the re-let stage."