When a Zipcar reservation, membership application, or account fee has been charged to the card on file, your bank may show the charge as pending or on hold. This is your bank's way of setting aside the spent funds while it prepares to transfer the funds out of your account.
Once the funds have been fully transferred from your bank, the pending charge or hold will be removed. This process can take up to 3 - 5 business days, but will vary by banking institution.