Social Impact Investors Group

The Social Impact Investors Group (SIIG) exists to support Foundations interested in starting or currently undertaking social impact investing. Membership is open to foundations and to organisations with a charitable or social mission with investible assets.

Social impact investing is defined by the OECD as “the provision of finance to organisations addressing social needs with the explicit expectation of a measurable social as well as financial return”. In practice this can involve a range of funding methods, from investing directly into frontline organisations or putting money into funds supporting a specific theme such as housing or ‘tech for good’, to participating in social impact bonds and ‘payment by results’ models.

The SIIG has been operating informally since 2011 resourced by an active volunteer Steering Group, including representatives from ACF, Esmée Fairbairn Foundation, Comic Relief, City Bridge Trust, Big Society Capital, Bank Workers Charity, Treebeard Trust and Trust for London.

Convened since April 2018 by the Association of Charitable Foundations, the SIIG runs a free programme of Market Information Days to raise awareness about social impact investment opportunities and a paid-for membership programme of learning sessions and resources. Members learn from each other and from more experienced foundations, allowing newcomers to build staff knowledge while reducing the costs of establishing a programme.

The paid-for membership programme includes a series of learning events open to all SIIG Members’ staff and Trustees, covering topics such as how to assess and balance financial and social return, how to carry out due diligence, and exploring different types of investment. The SIIG also provides a toolkit of templates and exemplars for those establishing or running a social impact investing programme, and signposting to a range of learning events run by external partners.

Market Information Days run every 6-8 weeks to educate attendees about the latest social impact investment opportunities from charities, social enterprises, social purpose organisations and social impact funds. The Days are mutually supportive with a focus on learning; newer investors learn from the questions posed by their more experienced peers, and those presenting are able to benefit from feedback on their ideas. The SIIG does not go further than providing a means for communication, any follow-up interactions or information shared relating to particular transactions is not the responsibility of the SIIG. 

The SIIG Diversity, Equity & Inclusion Charter contains concrete actions to improve diversity of thought and representation, ensure equity of opportunity and outcomes, and implement inclusive practice by broadening the range of experiences and perspectives we bring to bear in our processes and decision-making, to ensure better decisions are made. 

A full list of SIIG events is available in the ACF Events listing

To learn more about the SIIG and to join our mailing list, please contact:


Members can access the SIIG here

We support UK foundations and grant-making charities