Arthur Weller Replies:
Keep a record of all your rental income and allowable expenses (attributable to your rental business) from 6 April until the following 5 April. Then amalgamate all the income and expenditure and draw up an income and expenditure account for that period. Then complete the UK Property supplementary pages (SA105) of the Self Assessment Tax Return for that tax year and send it in to the Revenue on time. It is as simple as that.
You could try ringing your local Revenue office, or downloading the SA105 (Notes) from the HMRC website.