Social Impact Investors Group (SIIG)
The Social Impact Investors Group (SIIG) is a vibrant and innovative group that exists to support foundations interested in starting or who are currently undertaking social impact investing.
Membership is open to foundations and to organisations with a charitable or social mission with investible assets. SIIG is facilitated by ACF and led by a steering group from its membership*.
Existing members can access the SIIG members community here (login required).
Find SIIG events Learn more about the SIIG
To join or discuss SIIG membership, please email [email protected].
SIIG membership
“This is the best way to get an introduction to social investment and meet like-minded foundations." SIIG Steering Group Member
SIIG provides learning sessions, practical resources and networking opportunities. Whether you’ve just made your first investment, are thinking about if it is for you, or you’ve been doing it for years – this group is open to all. Members contribute through peer learning and collaboration, enabling more fellow foundations to feel skilled and supported to undertake social impact investing. The SIIG Steering Group* provides oversight and expertise, with activities co-ordinated by ACF staff.
During 2026, the SIIG is planning**:
- 10+ learning sessions for those new to the sector and more experienced
- Social Investment Showcase (formerly Market Information Day) – for networking and the chance to learn about investment opportunities
- Introduction to social impact investment sessions featuring investors and investees. Watch the session we held in March on demand. Passcode: 801z=7VC
- Our popular Impact Investing in the Main Endowment course with a new bitesize version for trustees – free only to SIIG members
- Regular SIIG e-newsletters with information on events and relevant news
- To represent SIIG members to policy makers and within the wider social investment landscape.
Fees and how to join
Membership fees to join the SIIG are
£1,000 per year for ACF members and £1,600 for non-ACF members. There is no extra cost to attend events and no restriction on the number of staff or trustees attending.
The SIIG is committed to improving diversity, equity and inclusion in social impact investment. Find out more in the
SIIG Diversity, Equity & Inclusion Charter.
All ACF members can sign up to the SIIG mailing list to receive updates on relevant news and events. Login to your account and update your preferences by selecting 'Updates on social impact investing'.
To join or discuss SIIG membership, please email [email protected].
*The SIIG steering group includes representatives from: Esmée Fairbairn Foundation, Barrow Cadbury Trust, City Bridge Foundation, Joseph Rowntree Foundation, Better Society Capital, Church of England, Barnwood Trust, Treebeard Trust and Trust for London.
**Information, communications and/or opinions shared at ACF and SIIG events are not intended, and should not be considered, as investment, tax, financial, or legal advice. Investors must make their own decisions, or seek independent advice.
