What coaching accreditation do I need for each age group?

Australian Athletics says affiliated clubs must ensure all coaches hold an active accreditation, recognised by the Australian Sports Commission. Coaches also need a Working with Children Check or a valid exemption. Its four track and field levels are:

• Youth Coach (Level 1): athletes up to 13 years old (the accreditation matrix legend says 12 and under). Aimed at coaches of athletes aged 3-12. You must be 16 or older. Generally about $270, with 7 hours of facilitated learning and 5 hours online.
• Development Coach (Level 2): athletes aged 12 and over, preparing for state-level competition. You must be 16 or older. Assessment is a planning assignment plus a practical coaching assessment signed off by an approved assessor. Generally about $360, with 16 hours facilitated, 12 hours online and 2 hours of assessment.
• Performance Coach (Level 3): athletes aged 16 and over aiming for State or National Championships.
• High Performance Coach (Level 4): athletes aged 16 and over targeting major international events.

Prices are set by each State or Territory Athletics Association. First-time accreditation holders get one year of complimentary coaching membership and insurance. Australian Athletics advises against training with non-accredited coaches, who are not covered by coaching insurance and cannot coach within affiliated clubs.

Sources: https://coachathletics.com.au/athletics-coaching-accreditation-standards, https://coachathletics.com.au/level-1-youth-coach, https://coachathletics.com.au/level-2-development-coach