Yeah I left out NI for brevity lol. TL;DR for everyone else, in the last couple years they changed the boundaries for NI to match those for income tax. NI is 0% for the first £12,500, 12% up to £50k, 2% over £50k. So really you can just combine it with income tax, and the total tax bands are 0%, 32% and 42%. This means the take home tax rate difference is only 10%, not 20% like commonly perceived with the 20% and 40% rates.

There's also some fuckery around the £120k mark, where basically you take home less as your salary goes up a bit. I forget the exact details, but you have to punch through to almost £150k for it to be worthwhile, or something.

Then there's salary sacrifice, which anyone earning over £50k should consider. Basically, you agree with your employer to reduce your salary, and the extra goes straight into your pension. When you do this with income above £50k, you avoid paying the 40% tax at that time. If when you retire your retirement income remains below the 40% tax bracket, then you'll never pay the 40%, only 20% when you withdraw your pension.

Yes, through loopholes.

An example, you may have heard of "Employee Owned Businesses", a system introduced by the Tories, modelled after John Lewis/Waitrose, which is an employee owned company. Essentially, under the scheme a privately owned cash-rich business can buy itself from its owners. This is done with the set up of an Employee Owned Trust (EOT), a separate business that temporarily owns the main business over however many years it takes to pay off the owners for the full price. After that, the business is fully employee owned and operated. However, the big incentive is that it's tax free for the original owners.

Say the business was worth £50 million. In theory you could restructure the business into an employee owned business, or sell it to anyone else, but you'd have to pay £10 million in capital gains tax, and you'd only take home £40 million. By going the EOT route you get the full £50 million.

Most high value transactions that are done use some tax incentive scheme or another to reduce the capital gains tax below the starting level of 20%. Such loopholes are not available for income tax. However, truly wealthy people don't make most of their money through salaries, their main income is capital gains.

Personally I don't think income should be taxed, at least not below some very high threshold (to prevent exploitation). You're already giving up your time, which is the ultimate value, and you're doing so in service of a business which itself is in service of society. You've done your part, you're not getting the excess profit. The things that should be taxed are when people make money from assets, when they make money not by doing things but by exploiting what they own.

I have almost no doubt that even current Labour would be a vast improvement.

A government that puts immigrants into boats or tries to ship them to Africa? This is insane. Even if you completely avert your eyes to this humanitarian menace, it makes zero fiscal sense. Current Tories are evil, by the very definition.

I'm assuming you mean for voting, the least important thing you can do, politically.

It doesn't matter much. Protest vote (if there's a good protest vote available to you), spoil your ballot (if there's something you want to say because it will be read by bored candidates), or stay at home (so that you don't add to turnout). In the vanishingly unlikely event that your local Labour candidate is an actual leftist, vote for them.

For more meaningful action, whatever works for you. Protest, direct action, letter-writing. In the vanishingly unlikely event that your local Labour candidate is an actual leftist, campaign for them (and turn out to support them when the leadership inevitably comes for them).

Just don't pretend that voting for the least worst option will give you better options in future. It will not.