BIM71015 - Computation of liability: basis periods - commencement years


The basis period for the first year in which a person starts to carry on a trade, profession or vocation begins with the date of commencement and ends with 5 April at the end of the tax year (or any earlier date of cessation).

The basis year for the second year depends on whether accounts are prepared to a date in the second year and the length of the period for which such accounts are prepared.

This table summarises the normal basis period rules which apply where accounts are regularly made up to the same date each year.



YearBasis Period
Year 1Date of commencement to 5 April in Year 1 (or to earlier date of cessation)
Year 2 (in which there is no cessation)
- where accounting date in Year 2 is less than 12 months after commencement12 months from date of commencement
- where accounting date in Year 2 is 12 months or more after commencement12 months to accounting date ending in Year 2
- where no accounting date in Year 212 months ending on 5 April in Year 2
Year 3 onwards (in which there is no cessation)12 months to accounting date ending in tax year (or 12 months to 5 April if accounts not drawn up to a date in Year 3 and there has been no change of accounting date)

If the trade ceases in the second or third year the rules which apply to the year of cessation are used, see BIM71025.

Different rules apply where there is a change of accounting date, see BIM71035.


Example 1 – where accounting date in Year 2 is less than 12 months after commencement

A new trade commences on 6 January 2007. Accounts are prepared for an 11 month period to 5 December 2007, and to 5 December in each year after that.

The basis periods are:


2006-2007Year 16 January 2007 to 5 April 2007
2007-2008Year 26 January 2007 to 5 January 2008
2008-2009Year 36 December 2007 to 5 December 2008

Example 2 – where accounting date in Year 2 is 12 months or more after commencement

A new trade commences on 6 July 2007. Accounts are prepared for a 15 month period to 5 September 2008, and to 5 September in each year after that.

The basis periods are:


2007-2008Year 16 July 2007 to 5 April 2008
2008-2009Year 26 September 2007 to 5 September 2008
2009-2010Year 36 September 2008 to 5 September 2009

Example 3 – where no accounting date ends in Year 2

A new trade commences on 6 January 2007. Accounts are prepared for an 18 month period to 5 July 2008, and to 5 July in each year after that.

The basis periods are:


2006-2007Year 16 January 2007 to 5 April 2007
2007-2008Year 26 April 2007 to 5 April 2008
2008-2009Year 36 July 2007 to 5 July 2008