I want to buy a new business but the only way I can do that is to increase the mortgage on my house. Will the interest I pay on the extra mortgage be tax allowable for the business?
In principle, yes, but there are restrictions to prevent improper use of this tax relief. Further restrictions are also proposed from 6 April 2013 (see above). Interest paid on loans used to buy into a partnership or to buy shares in a closely controlled company, or lend to such a company is generally tax allowable. However, it would be best to have a separate loan for this business investment, as when you repay any part of the mortgage the business part will be deemed to be reduced first. You will also have to hold at least 5% of the ordinary shares of the company and work for it for the greater part of your time.