Cuurent rate of tax on funds?

[TBS]

Perhaps there might be some temporary positive effects on tax revenues to the extent that such people do realize profits in taxable accounts initially (many may just invest fresh money), but at the same time the base of taxable assets will decrease versus what it would have been as the new NISA accounts are built up, with negative effects on revenues.

Maybe this is exactly their logic
It's a short term smash and grab to help balance the books now, as people sell existing taxable investments early to fill new NISAs. But depriving the state of tax revenues in future.

It's no problem for the politicians who made the decision now - they'll be retired and long gone before the chickens come home to roost

[captainspoke]

Not sure how important it might be, but for as many folks who do end up with some Nisa money in retirement (that cohort of savers/population), will likely have a better retirement than if they simply banked it (post-office'd it?), or worse, didn't save at all.

Since presumably they'll be spending it down then, some revenue will then come in as consumption tax. And at the same time, maybe less pressure/need to adjust pension payments upwards, since a hopefully wider swath of the population has become more self-responsible for their retirement years (= no increase in gov't outlays for that).