SIMIA was established in 1986 as a mutual insurance company providing professional indemnity insurance to firms of solicitors based in England and Wales. It was established in response to a drastic reduction in capacity for solicitors’ excess professional indemnity insurance together with an increase in the cost of that insurance. Its twin objectives were to secure the availability of professional indemnity insurance for solicitors; and to mitigate the cost of that insurance by ensuring the availability of capacity. SIMIA has succeeded in achieving both these objectives.

From its inception SIMIA has been quick to respond to the insurance requirements of its Members. It originally provided £0.5m of insurance to its Members in excess of a compulsory primary layer of £0.5m. In 1989, three years after SIMIA was established, the compulsory primary layer was increased to £1m and SIMIA reacted by increasing the level of cover it offered to £2m.  In 1990 SIMIA again increased the level of insurance it offered its Members to £2.5m and to £3.5m in 1991. The level of cover offered by SIMIA was again increased in 1992 to £4.5m, the current maximum level of cover SIMIA offers. In October 2005 the Law Society increased the compulsory £1m level of insurance to £3m for limited liability partnerships and to £2m for partnerships that did not limit their liabilities. SIMIA therefore became a Law Society qualifying insurer in 2005, which allowed it to continue to write insurance above £1m. It now offers insurance in both the compulsory and excess layers.

SIMIA has offered reductions on the premium it receives from its Members since 1989. The reduction is in the form of a deferred payment. SIMIA retains the right to request payment of the deferral from its Members. Solicitors' firms insuring with SIMIA obtain a reduction of 10% if they purchase insurance of between £2m and £3.5m; and 15% of the total premium if they purchase cover of over £3.5m. As a result of the deferral Member firms have saved approximately £30m since 1989.