HEFCE announced their Policy for open access in the post-2014 Research Excellence Framework (REF) in March 2014.
The policy states that journal articles and conference proceedings must be available via open access to be eligible for the post-2014 REF. This means that outputs must be deposited in an institutional repository, such as LSE Research Online, at the point of acceptance.
The policy applies to journal articles and conference proceedings with an ISSN accepted for publication after April 2016. The output must be deposited at most three months after acceptance. Embargo periods and exceptions apply where necessary. See below for more information.