The Google-backed fundraising platform, which has raised more than $21m in the last 18 months, is raising the fund as it commits to co-invest $4m in 'B Corporations'.

CircleUp, the US-based crowdfunding website backed by internet company Google among others, is seeking to raise $25m for a growth capital fund, according to an SEC filing.

Founded in 2005, CircleUp secured $14m from Google Ventures, Google’s venture capital fund, and several other investors in a series B round in March which followed a $7.5m Google Ventures-led series A round in May 2013.

SEC filings show CircleUp also raised $3.4m in funding across 2007 and 2008, and it secured $1.5m…