If the payment is attached to an invoice it first needs to be removed from the invoice in order to be deleted. Click here to learn how to remove the payment from an invoice.
Once a payment has been removed from an invoice or if it was never applied to an invoice then it can be fully deleted from the clients ledger.
Under the Unapplied Payments/Credits section of a client's ledger you'll see all payments that are not applied to an invoice and are able to be deleted.
Find your desired payment that you want to delete and click Delete in the Actions column next to the payment.
A user must have billing permissions to delete a payment. If it was a Credit Card payment then the user must be an admin to refund the payment.
An admin will be able to see the that the payment was deleted via the activity log.