Is it legal for my employer to deduct money from my final pay?

Not necessarily. The Wages Protection Act 1983 says an employer can only make deductions from wages if you have agreed in writing, or the deduction is authorised by law or a court order. For deductions relating to something like damage or training costs, the employer generally needs your written consent to the specific deduction, and it cannot make a unilateral deduction based on its own view. Even if your contract mentions repayment of training costs, the amount must be reasonable and properly explained, and the employer should follow a fair process. Write to your employer asking for a breakdown and repayment of the unauthorised deductions, referring to the Act. If they refuse, contact MBIE's mediation service or lodge a claim in the Employment Relations Authority to recover the wages.