Tax on US Treasury bill

Hello, I am going to buy a US Treasury bill (in USD) via a US based securities platform. I will hold the bill until maturity. So, my gain will be the discount of the bill. Is the gain subject to income tax rather than capital gain tax? What part I should fill in when I declare it in my self assessment? What exchange rate I should take into account to convert the gain in USD into Sterling? Best regards, Nancy

Hi,

The guidance at SAIM3010 explains the tax treatment of 'deeply discounted securities'. Where certain conditions apply, gains on such securities are subject to income tax (ie as Chargeable Event Gains).  
If your US treasury bill falls into that category, you would report the Chargeable Event Gain under 'Other overseas income and gains'  in the Foreign pages (SA106) of your self assessment tax return (with the amount in USD converted to pounds sterling using HMRC conversion rates).                                                            

SAIM3010 - Deeply discounted securities                                                                                                                            

Thank you.