What does 'Post Tax Ded 1' refer to on payslip?

[hyperborean]

What does the above refer to on a payslip? Appeared on a payslip of mine from mid year and can't figure it out. Same month I got a bonus and also paid extra due to revenue mistake with my tax credits the month before.

Thanks

 

[Setanta12]

Sounds like something that comes out of your wages after tax. 'After Tax Deduction 1'