There's rarely been a better time to be an Australian gas exporter.
The war in Ukraine has seen demand for Australian gas soar, and pulled prices skyward with it.
And Australia has plenty of gas to offer — it is one of the world's largest LNG exporters, and those companies selling gas to the world are in a prime position to capitalise.
The gas being sold is owned by the Commonwealth, and licensed to be sold by the companies extracting it.
So how much are Australian taxpayers making from the sale of Australian gas?
Right now, probably not as much as you might expect.
The windfall tax you've probably never heard of
As gas prices have shot up, there have been calls for Australia to try and capture some of that profit through a new tax on gas companies.
Comparisons have been drawn with countries like Norway, which places a 78 per cent tax on profits from its oil and gas companies (many of which are partly state-owned anyway).
Others suggest Australia just reform the taxes already in place.
Australia already has a special tax for offshore oil and gas projects, known as the Petroleum Resources Rent Tax (PRRT).
It taxes profits from those projects at 40 per cent, on the grounds they are commonwealth resources — so the Commonwealth should share in the profits.
But despite plenty of gas being sold, it brings in surprisingly little tax.
The tax has been around since the late 1980's, as Australia's oil industry was developing.
Gas is now a much larger industry than oil, but despite the industry's growth, the tax has been bringing in roughly the same amount of revenue.
The revenue isn't even keeping up with Australia's general economic growth, becoming ever-smaller against Australia's growing GDP.
And it is forecast to keep diminishing — falling from $2.6 billion this year, down to just $2 billion in 2025-26.
So why is an industry bringing in tens of billions of revenue, paying so little tax for the gas it sells?
A decades-old tax made for a different time
The tax was introduced in 1988 to try and capture revenue from offshore oil and gas projects, but back then it was mostly oil.
The aim was to try and both encourage companies to explore offshore oil and gas, and significantly tax the profits made.
Companies would only have to pay tax once the projects had entirely paid for themselves — that is, all the money spent exploring and constructing oil and gas wells and the associated infrastructure had been recouped.
That's a fairly normal circumstance — most taxes are only paid on profit.
But importantly (and controversially), those constructions costs grow over time, the same way interest grows and compounds in a savings account.
The scheme was designed to be remarkably generous, with interest of up to roughly 18 per cent applied to different elements of a project's costs, and allowed to compound.
For example, if a company spent $10 billion on a project, they may wind up being allowed to deduct $15 billion or more from their tax bill years down the track — because those costs have compounded.
Given the often remote location of gas deposits, projects can be eye-wateringly expensive.
As at 2020-21, according to tax office data, the industry was carrying a total of $283 billion in future tax deductions from expenditure.
The Gorgon gas project, built on and around Barrow Island off WA's north-west coast, reportedly cost $70 billion to construct.
With the PRRT's deductions scheme in place, there have been suggestions the project may never pay the resources tax.
Change might be coming
It seems increasingly likely the PRRT is set to change, in an effort to capture some more tax revenue from the sector.
Treasurer Jim Chalmers has singled out the tax as one area of possible change, whenever questioned on the idea of a "windfall tax".
There are a few voices suggesting some reasonably simple tweaks that they argue could make a big difference.
The Morrison government ordered its own review of the PRRT in 2017, and made a few changes basically reducing the deductions available — but they only applied to new projects, not those already underway and benefiting from the current boom.
The Australian Industry (AI) Group, a business lobby, argues changes need to go further and capture projects already operating.
It suggests that additional revenue should go towards funding the transition away from fossil fuels, given how expensive that process will likely be.
The AI Group's Tennant Reed said the tax clearly isn't working.
"There's no doubt that the deductions under the PRRT are quite generous," he said.
"And if those deductions were less generous, that existing tax would be raising quite a lot more money for the production and sale of Australia's gas and oil resources."
He said changing tax settings on existing projects is entirely fair — as it happens to people, and companies, all the time.
"While it requires careful action, altering the tax settings that apply to future income years is totally legitimate," he said.
"I'm more than 40 years into my asset life, and the tax settings have changed on me a bunch of times."
The gas industry argues there is no case for change, as the PRRT is doing its job.
Samantha McCulloch from industry body APPEA was asked on the ABC's 7.30 program whether she thought the current PRRT intake was fair.
"The PRRT is projected to provide $11 billion to the federal government budget (over the next four years)," she said.
"This is already a profits-based tax of at least 40 per cent, and its just one of the financial contributions of the industry to government revenues."
Different ideas for a booming industry
Others push for bigger changes.
The Greens would scrap the $283 billion in available deductions for gas projects altogether, and start charging producers the full rate of tax.
Progressive think-tank The Australia Institute suggests leaving the deductions, but restructuring the tax so it kicks in when "super-profits" are earned.
If gas companies have a particularly good year, only some of their revenue would be available for tax deductions – meaning some would be taxed no matter what.
In 2017, UNSW economist Richard Holden proposed adding to the PRRT with a royalties scheme, which would take 10 per cent of the revenue generated from projects.
Revenue is different to profit — it is simply the income made from selling the gas, with no consideration given to money spent extracting it.
Many states have royalties schemes in place for onshore mining and gas projects, but as offshore gas projects are in Commonwealth waters, no such schemes apply — which is part of the reason the PRRT exists in the first place.
Five years on, Professor Holden argues a better approach would be opening up more gas reserves to new projects, but requiring some of the gas produced to stay in Australia — pushing down gas prices for consumers.
"By decoupling some of the supply in Australia from the world's supply, you can decouple the price of gas in Australia from the world price of gas," he said.
"Now that doesn't do a lot for tax revenues, but it would do something to alleviate the price pressure that Australian households are under."
Has the opportunity for gas windfalls already passed?
Australia's energy market is already changing rapidly, and it is all but certain reliance on gas will steadily decline.
The Albanese government has made clear it expects gas to "play a key role as a transition fuel", but the presumption within that is it will decline as net zero emissions is approached.
Some experts expect that trend to be replicated globally — meaning no matter what sort of taxes are placed on the sector, the opportunity to earn significant revenue will fade.
Mr Reed said gas probably has another five years of so ahead of very strong prices, but the trend away will eventually arrive.
"If all our customers overseas do what they say they're going to do, those profits are going to fade over time," he said,
"There will be a mega-trend of lower consumption and probably lower prices."
Professor Holden said the prime time for gas exports (and tax windfalls) may already be behind us.
"The exact time path is unclear, but the writing is on the wall for coal," he said.
"I think gas is currently estimated to be around until at least 2040, in Australia, but there's no doubt that it will play a much less significant role in our energy mix over coming decades.
"That means less opportunity to tax it. So largely speaking, we've missed the boat."
