Open ended investment companies (OEICs) are a form of collective investment fund. OEICs are legally similar to investment trusts in that they are companies whose sole business is to manage the investments they own. OEICs operate more like unit trusts in that investors buy and sell shares in the OEIC from and to the OEIC manager rather than on the open market. This is possible as an OEIC can freely cancel existing shares (when an investor sells) or buy new shares (when an investor buys).

As with unit trusts, there may be initial charges and exit charges. However OEICS, unlike unit trusts, are generally single priced. As with any type of fund there will be an annual management fee.