Shared finances, defined as any situation in which a person acts as an observer of, partner in, or proxy for another person's finances, are an important but often unmet need for millions of customers. In the past three years, new entrants and disruptors have designed services to help people manage their shared finances, while banks have done little. This report outlines shared finances scenarios, lays out examples from firms that are designing for shared finances, and argues that digital business leaders should do more.