The 'Charges' area is found in the 'Finance' section.
Find the charge you wish to delete and press 'Edit.'
This will open the 'Edit Charge' screen which you can see in the image below. The 'Delete this charge' button is located in the bottom right hand corner.
When you click 'Delete this charge' a confirmation box will appear. You can then 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 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 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.'