Stock: valuation: non-allowable bases of valuation
Bases of valuation not acceptable for tax purposes
All bases of stock valuation other than the lower of cost and net realisable value and mark to market are not acceptable for the purposes of Income Tax or Corporation Tax on trade profits.
The notional replacement cost method (that is, a notional price at which the trader would have to buy stock in order to realise the normal rate of profit), BSC Footwear Ltd v Ridgeway  47TC495 is not acceptable but see BIM33135 for a description of an acceptable replacement cost method.
Following Patrick v Broadstone Mills Ltd  35TC44, and Minister of National Revenue v Anaconda American Brass Ltd (see BIM33120), PC1955, 1 All ER 20, the base stock (a predetermined number of units of stock carrying a fixed unit value, with any excess over this number being valued on the basis of some other method) and last in first out forms of valuation are not allowable for tax purposes.
A basis which `although in form made on a recognised basis, pays insufficient regard to the facts’ is not a valid basis of stock valuation. This is supported by comments made in Threlfall v Jones  66TC77 where Bingham LJ referred to the Anaconda case and then went on to comment on page 118 on Lord Radcliffe’s judgment in Owen v Southern Railway of Peru  36TC602 saying:
`He held, however, that the company must fail because its claimed deductions did not represent an accurate discounted assessment of what it might ultimately be liable to pay. In a sense, the company failed on the facts, not the law.’
Where a trade or business uses a non-valid basis of stock valuation and changes to a valid basis the principles established in the Bombay Commissioner of Income Tax v Ahmedabad New Cotton Mills Co Ltd.  case are relevant to the change, see BIM34000 onwards.