The attempt by Beth Brady to be paid up to $40,000 in overtime for seven months she spent out of work on incapacity benefits has failed on a legal point with the federal appeals tribunal saying she had been ''unfortunate''.

Ms Brady was just a few days into her new job, training to be a protective services officer at the AFP's Canberra College, in March 2011 when she injured her shoulder in a training accident.

She was forced to take seven months off work to March 2012 after surgery on the injury and was paid workers' compensation by federal workplace insurer Comcare for the period.

But Ms Brady took the case to the Administrative Appeals Tribunal after the insurer refused to pay out on $30,000 to $40,000 in overtime, night shifts and penalty rates the officer claimed she would have earned had she not been injured.

After completing her training in Canberra, Ms Brady was posted to the West Australian coastal town of Geraldton where she worked regular night shifts and overtime before going under the knife in August 2011 and spent the next seven months recovering.

A dispute arose with Comcare after the insurer decided that Ms Brady's compensation would be based on her $45,000 base salary and would not include the shift rates and other penalties that most protective services officers use to top up their wages.

Ms Brady appealed the decision to the tribunal, arguing that she was entitled to the extra money despite not actually working the overtime or night shifts because it was part of her ''normal weekly earnings'', as defined by Comcare's legal framework.

She told the tribunal that the shift and penalty rates had played a big part in her decision to join the force and that she had always intended to volunteer for every available shift and for lucrative overseas postings.

But tribunal deputy president Stanley Hotop has ruled that Ms Brady's compensation must be calculated based on the wages she was earning before she sustained her injury, not the period before she went for her operation.

''It is most unfortunate for the applicant that she sustained the compensable injury in the course of a training period during which she was in receipt of only a base salary and had not yet commenced to receive the night shift payments and overtime rates which she fully expected subsequently to receive, and did subsequently receive,'' Mr Hotop wrote in his judgment.