It is the $40 billion black hole that the Government is scrambling to plug.

And while the black economy is estimated to be worth as much as a fleet of 12 new submarines, no-one knows exactly what the figure is.

That is one of the issues the Black Economy Taskforce is grappling with, as it prepares to advise the Federal Government on how to combat the problem.

Taskforce chair Michael Andrew says the extent of non-compliance — by labour hire, cleaning and courier businesses in particular — is surprising.

"The thing that really struck me was the size and scale of the black economy and how endemic it is [to] every sector of the economy," Mr Andrew said.

Illegal cigarettes, gambling and phoenix companies are in the firing line, but there are some less obvious targets too.

What the Taskforce is targeting:

1. Fraudulent invoicing

"Interestingly, the most quoted ABN in Australia is Bunnings," Mr Andrew said.

Mr Andrew said many tradies hid their cash payments by fraudulently quoting the Bunnings ABN. ( ABC News: Armin Azad )

"Because every tradesman goes to Bunnings to buy their material and they have a receipt with Bunnings' ABN up the top.

"It means every plumber and electrician quotes the Bunnings ABN, so we can never trace who they are that are actually receiving the cash payments.

"When they're giving fraudulent invoices to people who they want cash payments for, they deliberately disguise this under the Bunnings ABN."

2. $100 notes

"Forty-six per cent of our currency in Australia is $100 notes. That means 14 for every adult in Australia. I'm yet to find one single adult who has 14, so where are they?"

3. The sharing economy (Airbnb, Uber, et cetera)

"The sharing economy is a big part of the problem," Mr Andrew said.

"You've got people going into business for the first time and they really don't understand the rules that every time you rent out an AirbnB it's taxable income.

"Every time you drive an Uber, it's taxable income. Every time you do a job on Airtasker, it's taxable income."

4. Sham contracting

"In WA, I think there's been a particular outsourcing of mining services and a lot of people are contractors that move from project to project," he said.

"That's more the nature of the economy here. We're starting to see legitimate people — employees — shifting to contracting.

Black Economy Taskforce chairman Michael Andrew.

"Being forced to, often by their employer, to avoid government charges and government tax, and they really are exposing themselves on work cover and other related issues."

5. Sales suppression software

"(It's) an accounting system that obliterates every time you get a certain receipt," Mr Andrew said.

"So, for example, it takes out all the $20 receipts that you might have had if you're a little restaurant or if you're a larger business. There's no audit trail behind it."

Mr Andrew said it occurred mostly in the restaurant trade, and had been banned in the federal budget.

"But we've been trying to track down where it is in Australia and there does seem to be quite a few examples in Perth," he said.

The Black Economy Taskforce is due to present its final report to the Government in October.