Most investments involve a signed, written agreement, and a bank deposit at some point (or schedule of bank deposits if you haven't started receiving funds yet). Verification is fairly simple to do. When it comes to your own money that you've put in it's not much different. If you're taking investments without precise documentation, you're a big risk. If you're loaning your own money to the company without a paper trail (co-mingling funds), this too highlights other risks. When it comes to investments in the form of partnership or non-monetary support, these two are important to document, whether it's a buying agreement, a co-marketing agreement, a purchase order, or whatever. (Precise) Documentation shows responsibility and accuracy which are two positive signs for additional investors. Have your non-disclosure agreement ready or it will also look like you haven't required it of anyone else. It's up to the potential investor what kind of verification they are seeking. Some may also want to have conversations with prior investors and may vet your story to see if you are sharing the same information and outlook with all investors, ask what persuaded them to join, and how they expect to recoup investment.