Willis is to move to a new UK headquarters in London at 51 Lime Street, opposite the Lloyd's building.
Willis said it would occupy the 23 storey tower of the new building, being designed by architects Foster and Partners.
The low-rise portion of the building will be sub-let, said the company.
Contracts for the Willis building should be completed within the next two months, with the company expecting to occupy the new offices in mid-2007.
