(a) A trader prepares accounts to 31 December each year. Identify the basis period for tax year 2020-21.

(b) A trader prepares accounts to 30 September each year. For which tax year will the accounting year to 30 September 2019 be the basis period?

Assume in both cases that the special rules which are used on commencement, cessation or change of accounting date do not apply in any of the years concerned.