Abstract: Embodiments provide processing of non-DDA transactions as Check21 transactions. In some implementations, a consumer registers a DDA account (e.g., a checking account) with a payment processing entity. The payment processing entity (e.g., or an agent or affiliate) generates a non-DDA account (e.g., a debit card account) and maps the new non-DDA account to the consumer's preexisting DDA account. When the consumer uses the non-DDA account at a point of sale, transaction information, including the non-DDA account information, is routed to the payment processing entity. The payment processing entity uses its mapping to identify the consumer's DDA account, uses the DDA account information and transaction information to generate a Check21-compliant check image, and clears and/or settles the transaction through Check21 channels.