Guaranty Trust Assurance plc was incorporated in June 1989 as Heritage Assurance Company Limited and registered by NAICOM as a non-life insurance Company. In the second half of 2002, Guaranty Trust Bank plc acquired a majority interest in Heritage Assurance, thereby increasing its paid up capital from N 3.6 million to N100.06 million, with a view to repositioning and transforming the Company. In December 2003 the company recruited key personnel from the insurance and financial services industry who took over the management of the Company. With a then Authorized Share Capital of N 750million, the company's paid-up share capital was initially increased to N 359million in February 2004 and has been consistently increased over the years to N12billion.
By December, 2005, the company's Authorized Share Capital was increased to N5billion in line with new minimum capital requirement while the company's Shareholders' Funds stood at N 6.29 billion as at December 31, 2007.
In July 2007, GTA became the first Nigerian Insurance company to receive an A+ risk rating from Agusto & Co., the nation's premier rating agency.