Reducing Hours at Work Tax Code

I'm reducing my hours from 30 to 20 at work as I'll be studying with the Open University full time and wanted to know if my tax code needs to be changed? I don't receive any financial support, minus tuition, from the Uni and can't afford to pay too much tax.

Hi Katie,
A reduction in hours does not affect your tax code, but you will pay less tax if your earnings reduce.
For anyone earning 100k or less you would normally be entiled to a personal allowance of 12570 for this tax year.
Income Tax rates and Personal Allowances
For further information.
Thank you.