The ACT's budget deficit for this financial year is forecast to blow out to more than $255 million, nearly triple what was originally expected.

Key points: The ACT budget deficit is projected to rise from $89.1 million for 2019-20 to be more than $255 million

The ACT budget deficit is projected to rise from $89.1 million for 2019-20 to be more than $255 million The causes include the ACT's shrinking share of GST revenue, and greater spending on hospitals and light rail

The causes include the ACT's shrinking share of GST revenue, and greater spending on hospitals and light rail The economic consequences of the coronavirus and recent natural disasters are likely to further worsen the deficit

And the bottom line may sink even lower when the financial damage wrought by the coronavirus and a summer of natural disasters is realised.

The projected deficit will increase from $89.1 million to $255.6 million, today's mid-year budget review predicts.

The ACT Government blames the blowout mainly on matters outside its hands, such as falling GST revenue from the Commonwealth.

The ACT's share of GST income shrunk by almost $54 million.

However, increased spending, particularly on Canberra's hospitals, and falling revenue from land sales also contributed to the worsening budget position.

ACT Chief Minister Andrew Barr said the main concern was the escalating coronavirus threat, which had prevented thousands of international students from returning to Canberra for the start of the semester and was also hurting tourism businesses.

"China's our No. 1 trading partner — our higher education system, our biggest export industry, and tourism are both going to be impacted, and the longer that goes on the bigger the economic cost," Mr Barr said.

January's bushfires, smoke pollution and severe hailstorm could also affect the ACT's finances.

But Mr Barr said the economy was very strong, and the ACT had the lowest unemployment rate in the country.

Sweeteners for seniors and sports lovers

Most of the extra spending in the review had already been announced, including a $60 million injection into Canberra's public hospitals.

That will largely deal with unexpected demand, including a surge in emergency patients and elective surgeries.

A top-up of public hospital budgets was the largest single increase in budget allocations this year. ( ABC News: Franklin Hood )

A new high school will be built in Molonglo, to be paired with the existing primary school, and funding was also provided to trial new bushfire-detecting cameras.

However, a few new sweeteners were unveiled today.

Eligibility for seniors' cards will be relaxed — from next year, Canberrans will qualify for a card when they reach the age of 60, down from 62.

And parking at Canberra Stadium will be cheaper, with pre-booked fees falling from $7 to $5.

Hinting at a possible election pledge to come, $200,000 was set aside for early work to find a site for a new stadium. Both the Civic pool and Exhibition Park were mentioned as possible locations.

Funding for "stage 2A" of the light-rail network, which will extend the line from Civic to Commonwealth Park, has also been brought forward.

Rather than the $1.7 million in capital funding that was to be spent this year, the Government now expects to spend $31.4 million.

Household rates reprieve

Mr Barr also suggested household rates bills would rise more slowly from the next budget in June.

He said the ACT faced economic challenges and the government wanted to support household spending.

"What people can anticipate from the budget in the middle of the year is that the rate of increase in rates will be significant reduced, and that we will put forward a new five-year tax-reform program that will continue to see stamp duty cut," he said.

"The prudent decision we made at budget time six months ago was to leave a lot in the kitty in terms of a reserve, in case this sort of situation arose."

The Chief Minister said Canberrans had already done the "heaviest lifting" to change the ACT's tax system.

"When we release our next five-year rolling plan … they can expect rate increases to be significantly lower than they have been over the last seven or eight years."

Liberals leader Alistair Coe says the ACT's worsening deficit is "staggering" given increasing revenues. ( ABC News: Alexandra Alvaro )

However, Opposition Leader Alistair Coe said the "significant blow-out" was extraordinary.

"This is a staggering situation for the ACT Government to be in, despite the fact that they've been receiving record revenue from every single source over the last decade," Mr Coe said.

"They're very good at raising money, very good at spending money, but not so good at getting value for money.

"Canberrans are not seeing the improvements in services they deserve."