Adjusting employment conditions: what are the employer’s options?

Sometimes it may be necessary for an employer to adjust the employment conditions of its employees. For example in the event the company is experiencing financial difficulties. Also, after taking over employees of another company, the acquiring company may need to align employment conditions of the new employees with company standards. Such adjustments could include cutting a bonus scheme, abolishing a lease scheme or changing leave schemes. What options does the employer have to change the employment conditions of employees?