Hi Amzcor,

You will need to download the custom layout designer to make any changes to the layout or add any additional fields including user-defined fields.
Please click on the link to download the designer.
https://www.sage.com/en-za/sage-business-cloud/accounting/add-on-modules/

Here is a video on how to Customise on the layout designer video: https://vimeo.com/217988410

For further assistance with customizing, you can contact a Sage Cloud adviser near you, however, they do have a fee that varies per advisor.
https://www.sageone.co.za/find-an-accountant/

Regards

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