The lowest rate for medical officers will be at the same military medical level (MML) and the same increment you currently hold at the higher rank.

If you're in the Reserves and not on SERVOP C, currently getting HDA and will continue to get it after 1 February 2023, you'll need to complete the AD288 to reapply for the HDA from 2 February 2023. If you're a member of the Permanent Forces, you won't need to reapply.