Hi,
On a foreign investment, the income is the difference between the purchase and redemption price after each has been converted to sterling on the day the transactions took place, so includes any foreign exchange gains. Any losses cannot be deducted.
You can see more information here:
SAIM3010 - Deeply discounted securities: introduction
If you invest in deeply discounted securities, put the difference between what you paid for the bond and what you redeem or sell it for in box 3 of SA101 (page Ai1).
Thank you.