Second Income on NHS Bank

ShadowWolf

Thank you in advance for any advice you can give me!
I'm about to start a new job away from the NHS in April, but have decided to stay on the NHS Bank at my old Trust as a radiographer. The bank contract is a zero hours contract, for whenever I'm able to pick up shifts, so as and when and not always guaranteed a shift. My new job is a 37.5hr contract, though as I mentioned is not with the NHS, but in the industry. 
As I've only ever worked in the NHS, I'm completely new to this sort of thing, and have no idea how tax works when you technically have a second income, nor how to deal with it, as it's not something any ever taught me, and I've not needed to learn until now.
How do I go about declaring any income I earn properly, and how do tax codes work? I've been told it's not worth me staying on the bank, but I don't want to lose the skills I've acquired, just in case I ever want to return to the NHS! 

ShadowWolf

Addition: Also on my new job's HMRC form, do I need to state this a second job? Or do I just say this is my new current job? My new job starts on April 20th, but the form mentions any job I've had after the 6th April.

[Deleted User]

Presumably you new job will command a salary of over 12500? In that case you would be wanting to utilise your personal allowances at that source. It’s your new current job. 

On the banking job you would have no personal allowances available and would lose 20% of your income in tax on the assumption that the income from both salaries does not exceed £50000. Don’t worry about what you have been told. The additional income from you bank work will be taxed in the same manner as overtime pay in your main job although you will pay less NIC.

Live update: chancellor just confirmed new personal allowance at 12570 and higher rate tax kicks in at 50270 from April.

csgohan4

Usually NHS bank work is taxed at source, unless you specify to pay you via limited company, will depend on the trust