How are deferred tax assets evaluated for impairment under IAS 12?

Under IAS 12, a deferred tax asset must be recognized for all deductible temporary differences and unused tax losses to the extent that it is probable that taxable profit will be available against which they can be utilized. At the end of each reporting period, the carrying amount of deferred tax assets must be reviewed. The entity must reduce the carrying amount if it is no longer probable that sufficient taxable profit will be available to allow the benefit of part or all of that deferred tax asset to be utilized.