Foreign exchange impairment

Goodwill is an asset of the subsidiary and, like all assets and liabilities of the subsidiary, it is converted at closing rate. But, of course, closing rate varies from last year to this year and the asset therefore needs to be recalculated each year Cost of acquisition in a foreign currency (I presume that's what your question means) again needs to be translated at closing rate Ok?

and what about impairment if it given in foreign currency as it occurs at y/e should it be converted at closing rate for goodwill calculated at y/e and what about goodwill at DOA it also includes impairment fig what rate this will be converted ?

Both at closing rate. That involves a total recalculation of the original goodwill calculation that took place at date of acquisition!