The ACT's switch from stamp duty to rates drove almost half of this year's rise in commercial rates revenue, despite government attempts to play down the impact of the taxation reform on businesses.
Forty-four per cent of the increase in commercial rates revenue came down to the reform, while 37 per cent was due to the growing number and value of commercial properties in 2018-19, new government figures show.
Since 2015-16, total commercial rates revenue has grown by about 30 per cent, with 58 per cent of that increase attributed to the reform.
The numbers came as the ACT Legislative Assembly's public accounts committee prepares to hold its first public hearings into commercial rate rises next month.
Commercial rates are tipped to hit $190 million as the ACT government moves into its seventh year of slowly replacing stamp duty with higher general rates.
Coupled with residential rates, that will take the total general rates take to a predicted $539 million, although an updated figure is expected in next month's mid-year budget update.
The year before the tax reform began the total rates take was $209 million, although taxes such as insurance duty (which raked in nearly $45 million in 2011-12) have been abolished and stamp duty has been reduced year on year.
The territory also abolished stamp duty for commercial property transactions under $1.5 million last year as part of the tax reform, which meant an estimated 70 per cent of commercial property sales no longer incurred stamp duty.
But more than 300 Canberra businesses were hit with a double-whammy last year after the ACT Revenue Office revalued properties in Phillip, Civic, Turner, Braddon and Fyshwick.
Some rates rose by $100,000, while one car dealer in Phillip said his rates tripled over the past year.
ACT Property Council executive director Adina Cirson said commercial properties on land valued above $600,000 now paid rates at 5.1675 per cent, which meant owners were paying the equivalent of a stamp-duty-like charge every year.
The Property Council has found commercial rates are around nine times higher than residential rates, with the highest marginal tax rate for commercial properties more than double what it was in 2012.
"Of greatest concern is the lack of visibility on which rates will be payable at the end of the 20-year reform plan," Ms Cirson said.
"Commercial properties above $1.5 million also remain subject to a five per cent flat stamp duty rate and there are no plans to further reduce the top rates for commercial properties within the current budget forecast period."
The government has repeatedly tried to play up the impact of rising property prices and the growing number of commercial properties on the rates revenue increases.
In an answer to a question on notice, acting Treasurer Yvette Berry said growth in the number and value of new properties contributed about a third of the increase in total commercial rates revenue in 2018-19.
A separate answer showed 2018-19 saw the largest jump in the number of commercial properties in four years, up 93 to 6146. In the past 10 years, nearly 900 extra business premises have opened.
ACT Chief Minister Andrew Barr told the Assembly last October there were about 2000 more businesses operating in Canberra than there were three years ago.
Mr Barr said at the time commercial rates would grow by an average of six per cent each year across Canberra from 2017-18 to 2021-22, "giving certainty to the commercial property sector".
But the tax reform, property values and property numbers are not the only factors pushing up rates.
Government figures also show about 18 per cent of the 2018-19 increase was due to wage price index increases that would have occurred in the absence of tax reform. Around 21 per cent of the increase since 2015-16 was due to wage price index increases.
Rates laws mandate an annual land valuation based on a property's unimproved value on January 1 each year.
The new valuation takes effect following a determination by the commissioner for ACT revenue on July 1 of the same year.
The valuation approach is a "direct comparison", where commercial land sales are looked at and a broad adjustment to all properties is made if there is evidence of a change in general commercial property values across the ACT.
There has not been a blanket increase in unimproved values across commercial properties for the last five years though, as there have been too few sales to justify the rise, the government said through the question on notice.
However, pockets like Braddon and Phillip have been adjusted as "unimproved values of some properties in these areas were out of alignment with market values, relativities within the precinct, and in comparison with properties outside of the precinct".
The ACT Assembly inquiry public hearings will be held on February 6-8, with another hearing on February 25 to be confirmed. Affected businesses can fill out out this survey until February 4.