An Accreditation Report is a web page hosted by AngelList that investors can use to confirm their accreditation status. Once created, it can be reused for any investment that requires proof of accredited status.
Accreditation Reports meet the SEC’s new 506(c) accreditation standard for investing in publicly fundraising companies. It also meets the lower standard for investing in privately fundraising companies (the biggest difference between the standard for public and private fundraising is the requirement to provide proof of your finances for public financings.)
Many lawyers also consider things startups have always done to require the new standard, e.g. announcing a financing at a demo day or closing a round after a major article leaks about their financing.