If a refund is issued to a client, then Stripe will need to pull back the transfer sent to your Stripe account for that session. Usually, Stripe will be able to pull the funds back from the available balance in your Stripe account. 

However, if the payment being refunded has been included in a payout that has already been initiated (ie. it is on the way to your bank account already) or if there is no available balance in your Stripe account, then Stripe may need to withdraw the funds from your bank account instead to cover the refund you have issued to your client.

You will not be left out of pocket if this occurs, as the original Payout including that session fee will still arrive in your bank account. You can view the date that Payouts are expected to reach your bank account by logging in to your Stripe Dashboard at https://dashboard.stripe.com/

This is the only situation where Stripe will need to withdraw any funds from your account, and in most cases, it will simply not happen as you will usually have funds available in your Stripe account at the time refunds are issued.

We have more information here about negative balances in Stripe.
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