When those who don't take a digital ID ... and for whom "work" is made illegal ... find ways to transact with each other ... those transactions won't yield any tax for HMRC.

Those without the ID won't have bank accounts to raid. Hypothetically we are talking about the emergence of a parallel economy. There will certainly be fewer bank accounts and less tax.

Absolutely. When people are pushed out of the formal system, they’ll find their own ways to trade, live, and work outside the reach of the taxman. The underground economy thrives where trust, not control, is key. Governments can either adapt or risk driving people further from the fold.