It's handled through customer.subscription.updated webhook.
If the customer does not pay the invoice before the due date, or sends an amount that is not automatically reconciled, the subscription becomes
past_due, acustomer.subscription.updatedevent is sent, and thestatusfield remainsopen.
https://github.com/laravel/cashier/blob/10.0/src/Http/Controllers/WebhookController.php#L63