Corrections Act 2004, s 68; Corrections Regulations 2005, reg 43
Yes, the prison can take out (deduct) money from your earnings for:
any property you’ve damaged
any fines or reparation that you haven’t yet paid (you can apply to have your fines “remitted”, which means wiped. For more information, see “Before prison: The criminal court process”
any child support you have to pay.
If you’re working outside prison on the work release programme, the prison will also take money off for your board (the cost of housing and feeding you as a prisoner) and the costs of travelling to and from work.