The ATO believes small business is the big culprit when it comes to compliance with FBT and it's on a mission to round up the missing millions, says specialist Paul Mather on the latest Accountants Daily podcast.

Mr Mather, who is founder of FBT Salary Packaging Solutions, said the tax gap with FBT – the difference between what the ATO collected and what it believed it should be collecting – was 22 per cent, the largest for any tax.

"We've got a $4 billion revenue take on average and there's about a $1 billion dollar gap," he said. "The ATO believes that gap is predominantly with small business employers who are not within the FBT system."

"The Tax Office acknowledges that tax agents are very good at working with income tax and GST with their clients, but not so good with FBT ... and they need to upskill a bit around FBT.