Seventy-year-old pensioner Philip Robertson has lived in his Ngunnawal townhouse for 18 years. In 2016, he paid $737.26 in rates.

But last year, his rates bill increased to $1085.89, before the $100 one-off rebate.

Mr Robertson's story is not uncommon. Rates all across Canberra are increasing as the Barr government abolishes stamp duty and moves towards a land-based method of taxation.

The tax reform began in 2012 and will eventually result in what the government says is a fairer, simpler and more efficient method of taxation.

But his issue is with the recalculation of rates that only applied to people who live in multi-unit complexes.

Before, rates for units and apartments were worked out by dividing the land value for the total complex by the number of dwellings first, which meant nearly all units fell into the lowest rating factor.

Now rates are calculated on the entire value of the block first, placing apartments in the highest rating bracket.

Mr Robertson ran the numbers using the new unimproved value of his complex, $2.098 million, and its unimproved capital value, $144,762.

Under the old system, Mr Robertson’s valuation-based charge this year would have been $428.50.

But because of the new formula, his valuation-based charge nearly doubled to $805.55.

That meant he paid nearly as much in valuation-based charges as his brother, who lives in a much larger, non-unit titled property next door.

His brother’s valuation-based charge for 2017-18 was $859.61, with his total rates coming to $1893.43.

Overall Mr Robertson’s rates increased by 47.29 per cent while his brother’s increased by 6.45 per cent.

He said it was clear unit owners were being treated unfairly by the new method of calculation.

"His rates  [valuation-based charge] basically is about 6.7 per cent dearer than mine but I think because of the restrictions placed on me I would glad pay that 6.7 per cent to have those unrestricted terms on my particular type of property," Mr Robertson said.

"My property is about half the size of his property and my residence is about half the size of his.

"He can put solar panels on his roof without any approval, he can have air conditioning without approval and he has basically very unrestricted use of his property.

"If I want to put solar panels on I’ve got to apply to my body corporate and they may or may not give me approval. I definitely wouldn't put an extension on my house because it wouldn’t be allowed under the body corporate rules. I don’t think it’s fair."

The ACT Legislative Assembly’s public accounts committee is set to scrutinise the rates recalculation, after thousands of unit owners signed a petition calling on the changes to be reversed.

The committee will is due to report back by the end of next month.

Mr Robertson has asked the committee to look at reinstating the old method of calculation, and refund unit owners who have paid extra under the new system.

"They should have left it the way it was where everyone gets a percentage increase which is the same, regardless if you’re in a house or a unit," Mr Robertson said.