The move follows the decision of US parent UnumProvident Corporation to change its identity to Unum Group. The three main business units will be known as Unum US, Unum UK and Colonial.
Unum UK will implement new corporate branding which has been provided by the US parent.
The new branding in the UK will be completed by the end of the year.
Unum provides group income protection insurance, critical-illness cover and life insurance.
By the end of 2006, Unum had over two million lives on its books. Last year, it paid total benefit claims of 285m, with more than 191m relating to income protection.