Form P50Z is to be used to claim back tax owed to individuals by HMRC on a flexible access pension payment they recently had if any of the following apply – the individual:
Has taken a pension flexibility payment which used up all of their pension pot and they have had a form P45 from their pension provider Has been unemployed for 4 weeks or more Is not claiming one of the following taxable benefits Jobseekers Allowance Taxable Incapacity Benefit Contribution based Employment Support Allowance Does not expect to go back to work Has retired permanently and is not getting a pension from their old employer Has returned to full-time studyThe form should only be sent after the fourth week of unemployment.
Details can be found here