To send a payment in iMessage you need to have an iPhone, the latest version of the Venmo app installed and the latest version of iOS downloaded (iOS 10).
If you’ve downloaded iOS 10 and you’re signed into your Venmo account, you can send a payment to anyone in the U.S. using iMessage! At a minimum, the recipient will need a web-enabled smartphone that can receive text messages (they don’t necessarily need to be on an iPhone). If they are not already a Venmo user, they’ll need to sign up before they can accept the payment. Please note that payments sent in iMessage expire if they are unaccepted after 3 days and the money is returned to the sender.
Please ensure that you’ve enabled the iMessage extension for the Venmo app. If you haven’t, you can do so by tapping --> tap --> tap in the bottom lefthand corner of the keyboard --> tap --> toggle Venmo to be green.