Separate rating factors will be introduced for houses and units for the first time, to help smooth out some of the huge rates increases seen by unit owners in the past two years.

Rates and land taxes are rising as stamp duty falls, in line with the ACT government's 20-year taxation reform set out in 2012.

But a separate, more recent changes to make unit owners shoulder more of the total rates burden instead saw some units pushed into the highest marginal rating category which in turn jacked up their rates well beyond the 11 per cent average.

The effect was especially exaggerated for large complexes with lots of apartments, prompting the architect of the reforms to last year declare they had "stuffed it".

To counteract that, the government has set out different marginal rating factors for unit-titled and non-unit titled properties - meaning units, townhouses and apartments versus stand-alone houses.

The rating factors were developed "to minimise as much as possible the number of ratepayers who pay more or less than the average increase in rates", a government spokeswoman said.

An analysis of the 2018 and 2019 rates rises for units shows about 30,000 properties will have an 11 per cent or less increase in their bill this year compared with 26,000 last year.

There are about 3500 extra units this year to charge rates to, which partly explains the increase.

The number of units facing increases above 11 per cent was 22,017 this year, compared with 22,412 last year.

But while about 1900 units had increases of less than 5 per cent this year, only 69 will see rises of that magnitude this year.

At the other end of the scale, about 745 units are in for rates rises of more than 25 per cent, compared with 609 last year.

But Owners Corporation Network president Gary Petherbridge said the changes failed to fix the underlying problem afflicting units in large complexes.

He said he and Strata Community Association ACT president Chris Miller had offered to work with the Chief Minister's office last year on a review of the rating system but they were ignored.

"Those getting massive increases in apartments in large complexes are immediately in the highest bracket - that hasn't changed," Mr Petherbridge said.

The organisations are so unhappy about the changes they are "pooling resources" with an eye to next year's territory election, he said.

"We're not pushing one particular party, or one particular result. This would not necessarily benefit the Liberals," Mr Petherbridge said.

Mr Petherbridge said the rates rises had united the commercial and residential strata groups, as both had been stung but in different ways.

Commercial rates have also increased astronomically in some parts of Canberra, as large pockets of land were revalued after a flurry of sales.

The budget flagged changes to the length of time the average unimproved land value will be calculated over, in order to level out any spikes which could push the property into a higher bracket.

Mr Petherbridge indicated he would consider backing independents, saying the ACT's Hare-Clark electoral system gave him cause for optimism.

"The current government isn't being fair," Mr Petherbridge said.

However the quota needed to secure a seat in the Legislative Assembly is 16.7 per cent, a hurdle too high for most independents to clear.