Salary structures are locked in - once an offer of employment has been made to the prospective candidate. The data is then seeded into respective payroll systems/ portals.
There is NO way that salary structures should be modified now just to suit business interests and goals. As far as COVID-19 pandemic is concerned - it really doesn't alter anything and salary structures are going to be same as originally agreed with the employees. It is illegal to change salary structure without the consent of effected employees.
Quick thoughts:
1. Please obtain guidance on new/ altered salary disbursement modalities from your local Labour Union office before rolling out any communication to the employees
2. Please obtain consent from the effected employees on their new/ altered salary structures with clear timelines
3. Please handle grievances in a professional manner, when you receive them and ensure closure
4. Many organizations are resorting to % salary cuts these days and that is happening on Gross components of salary