The charges area can be found within the Invoice section under Finance .
Find the charge you want to delete and press Edit.
This will open up the edit charge screen which you can see in the image below. The delete button is highlighted in red.
When you click Delete a confirmation box appears and you click Yes to delete or No to cancel.
If the charge is on a paid invoice, locate the invoice, remove the payment and then delete the charge. You can then add a new charge or delete the entire invoice. It is important to remove the payment from the invoice otherwise you will have a paid invoice with an outstanding balance of minus the amount paid.
If the charge is on an unpaid invoice it is fine to go ahead and delete it off the invoice by clicking edit beside the charge and then delete.