What is a retroactive TUE and how do I prepare for one?

Under the World Anti-Doping Code, athletes competing below national level can usually apply for a retroactive TUE (after the fact) rather than in advance. You may be eligible for a planned retroactive TUE if your sport is not on the in-advance list, you have not been notified of inclusion in the Registered, National or Domestic Testing Pool, and you meet none of the in-advance criteria.

Sport Integrity Australia (SIA) says to:

1. Have a medical file ready with the information a TUE needs, in case an application is necessary (SIA publishes TUE checklists of the medical evidence needed).
2. If you are tested, declare any medication you are taking on your doping control form.
3. If you are told your sample returned an adverse analytical finding (a positive test), apply to the Australian Sports Drug Medical Advisory Committee (ASDMAC) for a retroactive TUE.

Retroactive applications may also be considered for emergency or urgent treatment, or where there was insufficient time or other exceptional circumstances to apply before sample collection. Emergency treatment should be carried out as medically appropriate, and the TUE question dealt with after the issue is stabilised.

Preparing a medical file does not guarantee a TUE will be granted, and ASDMAC warns there are strict minimum evidence requirements for every condition.

Source: https://www.sportintegrity.gov.au/what-we-do/therapeutic-use-exemption/retroactive-therapeutic-use-exemption