i) Goodwill

Goodwill is initially recognised as an asset at cost and is reviewed for impairment at least annually. Goodwill is subsequently measured at cost less any accumulated impairment losses. An impairment charge is recognised in profit or loss for any amount by which the carrying value of goodwill exceeds its recoverable amount.

For the purposes of impairment testing, goodwill is allocated to each of the Group's cash-generating units expected to benefit from the synergies of the combination. Cash-generating units to which goodwill has been allocated are tested for impairment annually, or more frequently when there is an indication that the unit may be impaired.

For acquisitions prior to 3 April 2010 costs directly attributable to business combinations formed part of the consideration payable when calculating goodwill. Adjustments to contingent consideration, and therefore the consideration payable and goodwill, are made at each reporting date until the consideration is finally determined.

Acquisitions after this date fall under the provisions of 'Revised IFRS 3 Business Combinations (2009)'. For these acquisitions transaction costs, other than share and debt issue costs, will be expensed as incurred and subsequent adjustments to the fair value of consideration payable will be recognised in profit or loss.

ii) Computer Software

Costs that are directly associated with identifiable and unique software products controlled by the Group, and that will generate economic benefits beyond one year are recognised as intangible assets. These intangible assets are stated at cost less accumulated amortisation and impairment losses. Software is amortised over three to five years depending on the estimated useful economic life.

iii) Acquired Intangible Assets

Intangible assets that are acquired as a result of a business combination are recorded at fair value at the acquisition date, provided they are identifiable and capable of reliable measurement.

Amortisation is recognised in profit or loss on a straight-line basis over the estimated useful lives of intangible assets, other than goodwill, from the date that they are available for use, since this most closely reflects the expected pattern of consumption of the future economic benefits embodied in the asset. The estimated useful lives for the current and comparative periods are as follows:

• Brand names and trademarks 2 years in respect of Autocentres, 10 years in respect of Boardman and 15 years in respect of Tredz and Wheelies;
• Supplier relationships 10 to 15 years;
• Customer relationships 5 to 15 years; and
• Favourable leases over the term of the lease.

Amortisation methods, useful lives and residual values are reviewed at each financial year-end and adjusted if appropriate.