Implement Unit white-label debit card issuance linked to BaaS deposit accounts and configure spending controls

Steps

1. Create a customer (individual or business) and associated deposit account in Unit; the deposit account provides the funding source for card transactions and must be in an active state before card issuance is possible
2. Issue a debit card via the Unit card issuance API, specifying the deposit account ID as the linked account, the cardholder name, shipping address for a physical card or configuration for a virtual card, and any initial spending limits; Unit returns a card object with a card ID and masked PAN
3. Configure spending controls on the card object: set daily spend limits, monthly limits, individual transaction limits, and merchant category code (MCC) allow lists or block lists via the card limits endpoint; spending controls are enforced in real time at card authorization
4. Implement a real-time authorization webhook handler (using Unit's card transaction webhooks or a card authorization control integration) to receive pre-authorization events if Unit supports authorization controls for your program; respond with approve or decline decisions within the required latency window
5. Subscribe to card transaction webhooks to receive authorization, clearing, and return events; map each transaction to the associated deposit account and post corresponding ledger entries — debit the customer deposit balance on authorization hold and settle on clearing, reversing the hold and posting the cleared amount
6. For 3-D Secure (3DS) enabled cards, implement the cardholder authentication challenge flow by handling the 3DS authentication webhook if applicable to your card program configuration