This document summarizes a webinar hosted by GRI on enhancing sustainability reporting through external assurance. The webinar featured presentations from GRI, Bloomberg, and the G&A Institute on trends in US sustainability reporting, the launch of GRI's US external assurance study, and the value of assurance. Key points included that sustainability reporting is growing in the US, with GRI reporters outperforming non-reporters. Assured reports and those using the GRI framework also tend to outperform. The GRI guidelines help improve reporting quality and standardize disclosures.