AIBU to think I might get heavily taxed?

I see you are not getting a redundancy payment as under two years so the under 30k will not apply in your case

If you have two jobs you pay the same amount of tax as one job, just that it is split, your redundancy payment is separate though and up to £30k is tax free

You don’t qualify for statutory redundancy if working less than two years. Hence being paid for notice period, but no redundancy payment.

I think you have got confised between a redundancy paymemt and PILON (payment in lieu of notice).

Sounds like they have refused PILON, which is thier right, and are making you work your notice period. You should also be getting whatever your redundancy payment entitlement is as a lump sum at the end of the notice period. I woild speak to HR to clarify what your entitlement is.

You basically have two payrolls at the same time. Nothing rare with that. Lots of people have two jobs, or one job alongside a pension. You get one personal allowance and one basic rate band. So ultimately HMRC add all your income, deduct one allowance and charge tax on the balance at the appropriate rate. Whether you earn £25k each on two jobs or £50k in one job, in a tax year, your income tax bill is identical.

HMRC will probably keep your personal allowanc3 tax code with one employer and charge basic rate tax in full on the other. You can tell them which to apply your personal allowance to, or tell them to split it between employers. It’s up to you but you need to tell them what you want otherwise they decide. You also need to check that both employers aren’t wrongly giving you a full tax code and tell HMRC if they are. Best to communicate with HMRC rather than sticking your head in the sand and being landed with a big tax bill several months later.

It doesn't sound like redundancy? Have they actually used that terminology? It's sounds as though you've been given notice and they don't expect you to work. Redundancy is when the role no longer exists. Have you been asked to sign a settlement agreement?

What's the question? As stated you will have two overlapping periods of employment and would be taxed in both. Stating you new job is your primary employment will move your tax code but you would be taxed by both and have to pay any tax shortfall or get a refund for tax overpaid if your tax codes aren't assigned correctly which usually is the case with two jobs.

You'll pay income tax on all your income from either your new job or your old one. The rate depends on how much your total income is.

It'll be 20% on the first £37,700 and 40% above that, then it goes up again at around £125k, but I can't remember the rate.

There's bound to be an online calculator that can work it out for you.

Having said all that, I'm not convinced of the legality of paying redundancy pay monthly instead of in a lump sum. Might be worth looking into.