One time I got it back in my pay, the other time I had to deal direct with HMRC
I think you can only claim shit back for a tax year that’s completed, but on the 1st of April this year will be so you can go ahead and try!
I found it easiest just to go to the tax enquiry office. I filled in a form and they gave me an appointment time that day…(I lived round the corner though!)
I had all my documents like P 45s P 46s and all the rest, I.D and whatnot…
The nice wifey at my appointment worked out how much I was due back and they sent me a cheque…only trouble was I moved away before the cheque came so I had to get another and the whole process took months!
Normally it should only take 4-6 weeks from the date of your appointment for the cheque to be issued. Found everyone I dealt with to be very competent and courteous which was a small fucking mircale considering that you are dealing with one of the huge monolithic civil service entities…
Best o’ luck….