A system, a method, and computer-readable media for opportunistically authenticating a taxpayer. Specifically, embodiments of the invention leverage the fact that the user has possession of particular documents or access to certain information as evidence that the user is the person referred to in those documents or information. If the user provides sufficient evidence to authenticate themselves while providing the information required for the financial transaction, no separate authentication step may be required. At a high level, documents or other data imported in a first context (e.g., during the process of preparing a tax return for a user) are used as evidence of the user's authenticity in a second context.