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HMRC internal manual

Inheritance Tax Manual

Foreign property: valuation of assets: loss on sale of shares

The relief for loss on sale of shares (IHTA84/S178) also applies to foreign shares (IHTM34001). 

The procedure is the same for both UK and non-UK shares.

If necessary you can use one of the many currency conversion websites available on the internet to find the exchange rate at the date of sale and death.