I know that goodwill write down cannot be reverse for both GAAP and IFRS. But what is the conceptual reasons for it? Especially when IFRS allows reversal of write down for inventory and plant assets.

Thanks.

The conceptual reason for not allowing the reversal of goodwill impairment is to prevent capitalizing of internally generated goodwill. Internally generated goodwil is not recorded because it does not meet the definition of an asset because there was no past transaction in which it was acquired.

IAS 36 Paragraph 125 states the following:

IAS 38 INTANGIBLE ASSETS prohibites the recognition of internally generated goodwill. Any increase in the recoverable amount of goodwill in the periods following the recognition of impairment loss for that goodwill is likely to be an increase in internally generated goodwill, rather than a reversal of the impairment loss recognized for the acquired goodwill.