Surprise, surprise: "Stephanie", the guitarist in a band so successful that she makes $300,065 a year without anyone recognising her, doesn't really exist.

A spokeswoman for the Treasurer's office confirmed to Fairfax on Monday that the case study that appeared on the budget 2015 website and caused amused disbelief in the music industry this week was fictional.

A case study from the government's 2015 budget website showing deductions for a fictional Australian musician who earned $300,065 a year. Credit:budget.gov.au

By selecting 'Arts and Recreation Services' in a 'Small business tax relief' search on the government's 2015 budget website, users are presented with the example of "Stephanie [who] performs in a band that she runs as a small sole trader. Stephanie's taxable income in 2015-16 is $300,065."

Triple J and SBS presenter Marc Fennell brought her to public attention and from there music industry websites followed, with a mixture of bemusement and mock admiration for the miracle muso, who seemed to have cracked the secret to prosperity held close by pop uberstars.