Fed govt has 'black economy' in its sights

The federal government is planning a crackdown on the black economy after an investigation into the widespread use of illegal cash, according to reports.

The Turnbull government's May budget is expected to include measures to claw back lost tax revenue fanned by the "black economy".

Board of Taxation chairman Michael Andrew says Australians consider taking cash payments and not declaring it "almost a national sport".

"It's really large and unfortunately it's going to take a significant amount of work to turn around societal attitudes," he told Fairfax Media on Wednesday.