A type of authorised investment fund, regulated by the Financial Conduct Authority (FCA). Investors in a QIS will be institutional investors, such as life and pension funds. 

Quantitative easing (QE) is a form of monetary policy in which a central bank purchases longer-term securities from the open market to increase the money supply. This encourages lending and investment. Buying these securities adds new money to the economy and serves to lower interest rates by bidding up fixed-income securities. It also expands the central bank’s balance sheet.
Formerly a little-known term outside central baker circles, it’s become a standard form of policy since the financial crash of 2008-9.