In the event that a refund is processed for a client, Stripe may need to retrieve the corresponding payment from your Stripe account that was designated for that particular session. Typically, Stripe is able to reclaim the funds from your Stripe account's existing balance.
Nonetheless, if the payment set for refund has already been processed for payout (meaning it is en route to your bank account) or if your Stripe account does not possess an available balance, then Stripe might have to deduct the necessary funds from your bank account to facilitate the client's refund.
Rest assured, this action does not result in any financial loss for you, as the initial Payout, which includes the fee for that session, will be deposited into your bank account as planned. The anticipated date for Payouts to be deposited into your bank account can be checked by logging into your Stripe Dashboard at https://dashboard.stripe.com/
It's important to note that withdrawing funds from your account is a measure Stripe will only resort to under these specific circumstances and is generally avoidable if your Stripe account maintains a sufficient balance to cover refunds when they are initiated.
For further details regarding handling negative balances with Stripe, additional information is available here.