The presidents of both the ACT branch of the Property Council and the Canberra Business Chamber told a Legislative Assembly committee inquiry into commercial rates on Wednesday that a taskforce needed to be set up to review the system.

The committee is looking into numerous claims of valuations sending rates bills for commercial property owners soaring across the city, with witnesses also raising concerns commercial rates are charged at nine times residential rates.

Outgoing ACT Property Council president George Katheklakis and business chamber president Archie Tsirimokos separately told the inquiry a taskforce needed to be set up to review the commercial rating system, made up of representatives from industry, the government and the wider community.

Mr Katheklakis and Mr Tsirimokos were among several witnesses before the inquiry who also raised concerns the government's tax revenue was more than making up for the 20 year abolition of stamp duty, and owners were facing increases in rates in the order of paying stamp duty every year.

While the reforms were originally touted as being revenue-neutral, Chief Minister Andrew Barr has since suggested they would be broadly revenue-neutral in aggregate over the entire 20-year period of change.

Representatives appearing with the Property Council also backed calls for the ACT to establish an independent, arms-length Valuer-General to conduct valuations - rather than the government - a proposal both the government and opposition have rejected.

Both Mr Katheklakis and Mr Tsirimokos also raised concerns that due to the nature of the territory's commercial property industry, often owners were unable to raise leases to cover increased rates bills and tenants could be attracted to Queanbeyan.

The lack of transparency about rate rises was also a key concern raised during Wednesday's hearings, with owners and the peak industry groups telling the committee owners were facing annual bill shock, as there was no forecast of future years' bills.

Mr Katheklakis said the industry knew it had to pay rates, and expected them to rise each year - but without any forecast, owners could not know what their bill would be from year to year.

He said they were not expecting forecasts to be set in stone, but without any future trajectory of likely bills over the 20-year program, investors would reconsider investing in long-term commercial property in the territory.

"Investors need to have an understanding of where it's projected to go over the longer term; 10, 15, 20 years from now," he said.

"If you don't know rates increases then in three years, they will say we need to make adjustments over the next 20 years of the lease."

Mr Tsirimokos said he didn't believe stamp duty was an impost for commercial buyers, as the tax was deductible, but the rising rates were starting to reach a point at which investors would be reconsidering buying in Canberra.

Similarly, the Property Council's Belinda Ngo said commercial investors needed to know what the final resting place was for rates at the end of the 20-year process.

She said the ACT would soon be reaching a tipping point, where investors would tell the council if rates kept increasing at current rates (about 7.5 per cent per year), they would no longer be able to invest in Canberra.

ACT Property Council chief executive Adina Cirson also said that, should a taskforce be created to review the system, the current increases on commercial rates should be frozen while industry and community could have an open, honest discussion about them.

Richard Snow, the head of property at the Snow family's Capital Property Group, also appeared, making a comparison of the taxes and rates in Sydney compared to Canberra. He said in Sydney land tax and council rates were about 2.6 per cent of the unimproved value of a block.

But he said in the city in Canberra, once rates, land tax, the city-improvement levy and other taxes were taken into account, it came to about 6 per cent of unimproved land value, almost triple the Sydney costs.

The inquiry continues.