Well, in Australia's case – the wage subsidy comes from the Australian Tax Office (ATO), which is our equivalent to the IRS. So if you haven't been withholding income tax from your employees, you can't get the subsidy for them (unless you confess your past tax evasion, which obviously you aren't going to do.)

But, paying employees cash only is much harder than it used to be. Many customers now only want to pay card. The tax office sees the card payments coming into your bank account, if you try to pay your employees cash it is easy for them to catch you. So, I think the number of workers actually hurt by that is relatively small.

COVID-19 has accelerated the transition from cash to card payment, because the health advice was to avoid cash payments (due to risk that cash may spread Coronavirus), and many businesses responded by refusing to accept cash entirely.