This excerpt taken from the VOD 6-K filed Mar 8, 2006.
Impairment review performed under US GAAP
No impairment is expected to be recorded under US GAAP due to a different methodology under US GAAP when compared to IFRS.
Under US GAAP, Vodafone tests finite lived fixed assets for impairment using a two step process. The carrying value of each operating company is first compared to its respective recoverable amount. The recoverable amount is determined based on undiscounted cash flows. Secondly, if the carrying value exceeds the recoverable amount, then the carrying value is reduced to its fair value, which is generally determined using discounted cash flows.