Hi,
The guidance at
SAIM2440 is based on the legislation at https:
Income Tax (Trading and Other Income) Act 2005, Section 370 and advises that "Interest ‘arises’ when it is received or made available to the recipient. Interest has been made available if it is credited to an account on which the account holder is free to draw".
If you are able to withdraw funds from the account at any time during the term, then the interest is taxable in each year that it arises.
If you have no access to the funds in the fixed rate bond until the bond matures, then you are taxable on the interest only in the tax year the bond matures.
Thank you.