Patent amortization (AXT exam March/June 2017 Section B Q5a)

Hi tutor,

Regarding this question

(a) Explain, with supporting calculations where appropriate, the corporation tax treatment in the year ended 31 March 2017, of the goodwill and the patent acquired by Borage Ltd.

– The patent was being amortised in Achiote Ltd’s accounts on a straight-line basis over a ten-year period.
– Borage Ltd will continue to amortise the patent over the remainder of its ten-year life.

The question suggests to amortize the patent over a 10yr period. May I ask why a 10yr period is allowed? Shouldn’t it be a 25yr period if it elects for a 4% pa allowance? Can a company choose whatever period they want to amortize an IFA? Thanks.