The above post is correct and amazing that it's taken 45 posts of random analogy, heated argument, spurious opinion and the occasional usefully considered reply for someone to point out an actual fact.
This is something that is covered by the government issued FAQ that anyone who should be aware of before either employing a FDH:
Q3.6 Can an employer deduct the helper’s wages to compensate for damage to
goods caused by him/her? What other items may an employer deduct
from the helper’s wages?
A An employer can make deductions for damage or loss to the employer’s
goods or property directly attributable to the helper’s negligence or
default. In any one case, the sum to be deducted shall be the cost of the
damaged item, subject to a limit of HK$300. The total of such
deductions shall not exceed one quarter of the wages payable to the
helper in that wage period.
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It's good to see that the problem has been resolved, but having lurked on the helper forum for some months now, this thread is an example of why I generally avoid posting- the useful info to uninformed BS ratio is just too skewed.