For anyone working, it's cost neutral, because they'll be paying an equivalent amount of tax on the currently tax-free band. Higher rate tax threshold is tied to the 20% band, so if that starts lower, so does the higher rate, and that presumably will fund the payment to people currently not earning enough to pay tax.
Annnnd yet it’s NOT cost neutral because of the cost of collecting and distributing the money. The cost of just collecting the money would be £13.75/person. So straight up there’s a loss of £9.75/head JUST TO COLLECT THE MONEY- if you presume there is a similar cost to pay the money, then you’re talking £22.50 loss per person to collect and pay the money.
There are approx 30 million tax payers, of which approx 5 million pay the higher rate including around 400,000 paying the highest rate. So 5 million people paying an additional 20% on the lowered 40% bracket equates to another £2,500/person collected as well as another £625/person on the highest rate. That makes, after a £22.50 loss/person, another £12.75bn collected. Once again at a cost of £140 million to collect and distribute. So that leaves £12.61bn left over. To fund approx 30 million getting paid £2,496/year. Which is a cost of approx £75bn.
You’re about £61bn short of change there.
If you want more tax to distribute as benefits why are you increasing tax to pay out to everyone £2,496? That’s just stupid. If it’s about redistributing money then just our and out tax more and increase benefits. That way at least you’re not wasting money paying money back to people it’s not intended to assist. But given as the top 1% already pay 28% of all income tax, I’m not sure just how redistributive you imagine income tax should be.