The partnership's turnover increased from £63m last year to £105m in the year to 30 April.
Clare said: "The key enabler of this high growth rate is our willingness to invest in the business. We are now able to assist our clients wherever they go in the world."
The new IT systems will link EC Harris' 40 offices around the world with "real time" connections, enabling staff to communicate over the internet. The firm's services will also be posted on an intranet to give all clients access to the same information.
A spokesperson said: "This will mean that wherever the client is in the world, they will have a single, consistent service, which is vital for our global growth plans."