If your P60 is showing a negative tax deducted figure, where you enter this depends on whether it relates to tax deducted during employment or after employment has ended:

• During employment (usually through a PAYE code) – enter the employment as normal on the employment pages and enter the negative value in box 2. This will then be netted off against the other employment pages in which the tax was originally deducted.
• After employment has ended (refund from HMRC or the Jobcentre) – enter the figure in box 1 at the top of page 6 of the Core Return (HMRC Forms mode).