Capital Gains Tax on Foreign Investment

For capital gain tax calculation, what should be the purchase price used if I only sell partially of my holding position? Would it be weighted average price or using FIFO method (First in First Out)? If weighted average price is used, how should I calculate the average price for non-GBP stocks and investment with FX effect? For example If I buy 100 shares of A stock at USD 10 dollar ( GBP to USD at 1.25) and buy another 100 shares of A stock at USD 11 dollar (GBP to USD at 1.23). Later, I sell 50 shares of A stock at USD 11 dollar (GBP to USD at 1.2) Should I use A or B to calculate the Capital Gains? A) Capital Gains = USD 11-(USD10*100shares+USD11*100shares)/200shares= USD 0.5 * 50 shares * 1.2 (FX rate) = GBP 30 OR B) Capital Gains = USD11*50shares*1.2(FX rate)-(USD10*100shares*1.25(FX rate)+USD11*100shares*1.23(FX rate))/200shares*50shares = 660-650.75 = GBP 9.25

Hi,

You can see guidance below, in paticular, the reference to the S104 holding : 

Shares and Capital Gains Tax (Self Assessment helpsheet HS284)

Thank you.

Hello, I understand the S104 holding now. What about the FX effect when I invest in foreign securities? Should I convert the FX amount into GBP amount whenever there is transactions for the cost and gains? Or should I just convert the foreign amount gains into GBP amount at the end of calculation? And please advise what FX rate I shall use? Is there a reference rate I could use from HMRC website or any reliable sources (international banks, Bloomberg, brokerage firms) are acceptable?

Hi nelk24,
You can use any rate within the relevant tax year.
The official exchange rates can be found here:
https://www.gov.uk/government/collections/exchange-rates-for-customs-and-vat
Thank you.