Confirm that card account updater (CAU) is automatically enabled for US-issued Visa, Mastercard, American Express, and Discover cards stored as PaymentMethod objects — no opt-in is required for most accounts
Register a webhook handler for payment_method.automatically_updated; the event includes the PaymentMethod ID plus the updated card fields (exp_month, exp_year, last4)
For legacy Card or Source objects, listen for customer.source.updated instead of payment_method.automatically_updated
In your handler, update any internal records that cache card details (last4, expiry) to reflect the new values from the webhook payload
Verify a subscription is using the updated PaymentMethod by checking GET /v1/subscriptions/SUB_ID and confirming default_payment_method matches the updated PaymentMethod ID
Test CAU behavior using Stripe test mode with test card number 4000 0000 0000 0010 which simulates a card-updated response
Known gotchas
CAU is broadly supported for US-issued cards but coverage varies outside the US — do not rely on it as the sole recovery mechanism for international customers
Network tokens (a related Stripe feature) provide more comprehensive automatic updates than CAU alone and are enabled separately; they emit payment_method.automatically_updated as well
Stripe does not guarantee a CAU update will occur before the next billing attempt — if the card expires between billing cycles, the charge may fail before the update arrives
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