How much can a landlord increase the rent and how often?

There is no set cap on the size of an increase in New Zealand, but there are rules on how it is done under the Residential Tenancies Act 1986. Rent for a periodic tenancy can be increased only once in every 12 months, and the landlord must give at least 60 days' written notice of the increase. For a fixed-term tenancy, the rent can be increased only if the agreement provides for it. If you believe the increase is excessive, you can apply to the Tenancy Tribunal to have it reviewed, and the Tribunal can set the rent at a level that is not more than the market rent for comparable properties. Apply promptly, since there is a time limit after receiving the notice. Compare the rents for similar properties in your area and keep the evidence.