Flexibility: you can choose when you work and, depending on the agency or school, accept or decline assignments.
Better work-life balance: supply teaching can reduce some of the workload associated with a permanent teaching post, such as long-term planning, marking, parents' evenings and departmental responsibilities.
Variety: you can work in different schools, year groups and settings, which can be useful for gaining experience.
Try before committing: it allows you to experience schools before deciding whether you want a permanent position there.
Potential route into permanent work: schools sometimes offer permanent positions to supply teachers who have performed well.
Useful for career changes or returning to teaching: it can provide a gradual way to return to the classroom after a break.
Less long-term responsibility: short-term assignments generally mean you are not responsible for a class's long-term curriculum planning or progress in the same way as a permanent teacher.
Networking: working in different schools can help you build relationships with headteachers, senior leaders and other teachers.
Experience for ECTs: supply work can expose early-career teachers to different school environments and behaviour-management approaches.
Opportunity to increase or reduce hours: depending on local demand, you may be able to work several days a week or just occasionally.