Collect your tenancy agreement, rent-increase notice, previous rent details, payment records and any messages with your landlord. Use the RTB’s current online reporting or dispute-resolution service, explaining when the tenancy began, when the rent changed and why you believe the permitted limit or notice requirements were not followed. Check the RTB website for the correct process, as the rules can depend on the tenancy date and the legislation applying at that time. The RTB will assess the evidence and decide any dispute or enforcement matter; consider getting advice from a solicitor or a recognised housing advice service if the issue is complex.