AMP New Zealand Office Trust says property tax changes announced in the Budget will hurt its profit from the 2012 financial year, by about 7% - 9%.
In addition, the Trust says it is unclear whether the tax changes will have an effect on commercial property values.
Meanwhile, the value of the Trust's portfolio has decreased once again, but the property investor says the worst of the declines is behind it.
The Trust says the value of its 15 office buildings fell 8% to $1.27 billion.
It has also delayed an investor vote on planned changes to the way it will pay its manager by two months, until late August, saying a review of the changes is taking longer than expected.