"We aim for e-tax to be available for Mac users from July 2013 and have partnered with DWS to achieve this, " the spokeswoman added. Government tender documents reveal the tax office paid Melbourne IT company DWS $5,220,668.82 to get e-tax working on Macs. Of that, about $4.9 million was spent on "software maintenance and support" and $279,320.46 on a feasibility study. Similar tender documents reveal that the Tax Office has spent a total of $32.3 million on developing and supporting the Windows version to date. Before now, Mac owners could use e-tax only if they first purchased a Windows operating system and then installed it on a partition of their hard drive using Apple's Boot Camp software, which enables a Mac user to dual boot their computer into either the Mac OS X or Microsoft Windows operating system. Alternatively, Mac users could purchase Windows and choose to use Parallels or VMware Fusion software that allows Windows to be run in an on-screen box within the Mac operating system.

The cost of the software, if used for tax returns, was tax deductible. Russell Ivanovich, co-founder of Mac and iOS (iPhone/iPad) software development company Shifty Jelly, said it was impossible to say whether $5.2 million was excessive, but said it sounded "expensive". "I doubt you'd find anyone anywhere that would call that a bargain," Mr Ivanovich said. Peter Wells, editor of Apple fan website MacTalk.com.au, said: "For software this complex and this important I think six figures is a totally fair amount, but I have no idea if seven figures is a fair amount," Mr Wells said.

"But to be honest, I think that they probably should have spent that money on a web-based system, because all they've got now is a Mac application when there are more iPhone and other iOS devices [like iPads] ... in this country right now than there are Macs on desks." Regardless, Mr Wells said it was great that a Mac version was coming – "but it's almost like [the Tax Office has] finally caught up to where they should have been in 2007". "They've got a hell of a long way to get to 2013." According to Gartner, 16.8 per cent of all personal computers sold in Australia in the first three months of this year were Macs. For almost a decade, Mac users had been lobbying the Tax Office to allow them to file their tax returns online.

In 2004, Labor Senator Kate Lundy asked the Tax Office's then commissioner Michael Carmody about whether a Mac version was coming. Mr Carmody told her that a Mac version would be "costly" to develop and that there had been "very marginal demand" for such a version after regularly surveying users. "It does not seem to us to be a good use of taxpayers' funds to bear that cost," Mr Carmody said at the time. Later, in 2007, the Tax Office said it would "redevelop e-tax to make it compatible with any computer system that has internet access". It would "test this with a small group of users in 2008, aiming to make it available more broadly in future years — pending the success of the trials". A year later the trial appeared to collapse, after the Tax Office said "the project identified a number of challenges and complexities" that were "so significant that the Tax Office is not in a position to offer a redeveloped e-tax product for testing in 2008". In July last year, the Tax Office told Fairfax a Mac version of e-tax had been developed in 2011, but because of a "number of complexities related to IT security concerns and usability" its release had been postponed until 2013.

E-tax was first released as a software package in 1997, when it was distributed at the request of taxpayers on CD. Since 1999, the number of tax returns lodged through it has risen from 13,500 to 2.6 million in the 2012 financial year. On Monday a Tax Office spokeswoman said technology developments and advancements now available had "provided the robustness and stability required for e-tax" to work on the Mac operating system. It said there would be a "future requirement for a web-enabled online tax return lodgment service" that would allow most operating systems to access it. But that this wasn't yet ready. "Our intention is for e-tax to be web-based in the future," the spokeswoman said. Earlier this month, Fairfax reported that the Tax Office was planning a systems overhaul to include mobile phones and social media, in order to enable taxpayers to do business with it any time from any device.