[fleddr]

I'm a dutch native and can give some background on the "black money". Growing up in the 80s, it was everywhere, in every sector. You could work a factory job and in part be paid in untaxed money.

Now that society is a lot less cash based, this practice is very uncommon as it comes to wages in normal jobs. It still exists in exactly the type of work you describe: any type of contracting where a private individual (home owner) is the client. Cleaners and gardeners working for private individuals may also be entirely paid this way.

These last remaining pockets of untaxed money continue to exist as the cost of regulation is higher than the reward. For example, cleaners typically do it as a side job, and they'd simple stop cleaning altogether when taxed on their low income. So it's better to just tolerate it.

Further, black money is considered spending money. You can't really hoard it and buy a house with it. You'd have to explain to the IRS where this money comes from. So it's considered "extra" money, money to directly spend in the economy, so it flows back in any case.