Because there’s no tax benefit of a GIA (unlike a pension or an ISA), you may have to pay tax on any income and/or profits your investments make. Whether you pay tax, and how much you’ll have to pay, depends on your personal tax circumstances.
You’ll be sent an annual tax summary to help you understand the tax you may need to pay for your GIA investments. If you have tax to pay, you’ll need to arrange this through your annual self-assessment.