This article will show you how to see invoices and credit notes together on the same list.
Firstly you need to have access to the settings in Clik Service.
To access these, go to Settings > Settings and the below window will appear.
Now select 'Sales orders/invoices/credits' under the modules tab in the left-hand menu.
Next, check there is a tick in the box that says: 'Show invoices and credits in combined lists (CRM activity and main invoice list)'.
Then click 'OK'.
Now you'll be able to see all your invoices and credit notes together, just select the Invoice module and any credit notes will be highlighted in red, like below.