It doesn't make much sense scrapping cash ISAs and "forcing`' people to invest. People would just buy bonds.
They mostly buy US company stocks.
HMG tax purchase of stock in UK companies. It's only 0.5% but when returns are normal, like 2%, it matters..
Less ISA availability would increase money going into pensions. "Storage" in those is net tax free (within limits etc).
But the pension funds don't invest in business when the bond yields are high, like now. When they're low they get hit by the tax too.
She's put CGT and Dividend tax up too which reduces incentive further.
The financial industry finds ways around things.
You can currently invest tax free, it's called "betting" (Spread betting) ONLY so it's not taxed. She'd have to close that off too. AFAIK it's a British quirk, as are ISAs.
Why SHOULD anyone invest in British companies? Apart from banks, many of these are dependent on overseas companies anyway
(FTSE 100 ordered by annual growth).
Sure I have some IAG SA ( not British, obviously!) and UK banks (they were ridiculously cheap on P/E) but I could name a dozen US companies which make these returns look very ho-hum. (And Notchy, spot the manufacturers..)
MBKs bonds return 4.5 - 25% depending on quality.
e.g. two here
Predictable Murrican stocks do this. I had to wait 2 whole weeks for it to move, but here £100 becomes £264.03. (3PLT dashed verticals are day intervals)
STock bought on the London exchange. (It will go a lot higher, by the way as will Bitcoin, - probably)
Personal tax would be 45% as income, it's still only going to be 24% as CGT. If they chase that, one could use the Cayman islands, bitcoin, Spread betting, all sorts of shenanigans. The people who earn most are best at avoiding paying tax, so don't push it, Rachel dear, or I'll copy what they do, as will everyone else.