Your employee should contact their QSuper claims manager to discuss their options. Their claims manager will consider the medical evidence and work with you, your employee, and their treating medical practitioner to develop a Graduated Return to Work Agreement (pdf).
When the arrangement starts, you'll need to deduct contributions at the employee's nominated percentage, based on the reduced salary. When the employee starts work on a reduced income, standard member contributions and compulsory employer payments must reflect the reduced salary.
On your contribution payment file, record the normal standard full-time hours, reduced standard base hours, and reduced hours worked.