Hi,
If you have no more live employments and think you will not be receiving any more taxable income in the near future, you can apply for a in year tax repayments using this link -
Claim back Income Tax when you've stopped working (P50)
If you think you will be starting employment again soon then it will be easier to deal with it via your new employer.
If that is the case once you have receievd your first pay you can contact HMRC so we can review the information we hold for the year and issue a new code to them.-
Income Tax: general enquiries
Thank you.