Can my employer make a deduction of salary if I am not at work?

The general position is that if you have no good reason why you were absent from work, then you are not entitled to be paid for the time that you were off.

Most employees who take time off work will, however, have a good reason, for example, you cannot get to work because of travel disruption or bad weather.  Even so, you are not automatically entitled to be paid- unless there is provision in the contract of employment obliging continued payments in such circumstances, or where there is a collective agreement or custom and practice of making such payments.

If you are not at work due to a period of sickness, then different rules apply.