I'm employed at the same place for 8 years and 2 months. Our salaries has always been structured in the following way:
Basic 75%
Bonus 25%
This month our employer decided to cut our salaries with this 25% because our Company in in a loss situation. We weren't consulted we were just told this is going to happen.
It will depend on your employment contract, should it indicate that your salary is structured as you mentioned without provisions you will have a case. On the other hand, salary is 100% thus in essence our salary is not paid in full, this constitute a unilateral change in employment conditions, same, that is unfair labour practice. You will have remedies but firstly let's explore your contract of employment. What does it say?