PMU means Permanently Medically Unfit. This doesn't always mean forever, it means at this point in time and until a particular issue is satisfactorily resolved, unless the condition is an outright bar to further service, in which case it is forever and non-negotiable unless you can prove the diagnosis incorrect. Sometimes there is a mandated period following a condition/injury to allow for full recovery which must elapse before you can be passed fit. You cannot appeal against the mandated time declared. TMU means Temporarily Medically Unfit. This means we need to find out more before declaring you fully fit or PMU. For example, if you were prescribed an asthma inhaler two years ago, you are TMU until we find out when it was last prescribed then declared PMU until you are fully free from prescriptions for four consecutive years. You are NOT made TMU for two more years, you would be PMU until four years free. There's a difference. The reason you are not TMU is because you could have a recurrence of the condition tomorrow and the clock would have to start again.