The invoice style as displayed in SimpleClinic can be changed from a default layout to a "fancy" layout and perhaps other styles in future.

The web portal invoice style can also be changed to a different layout.

Both invoice style settings (being the in-clinic invoice and web portal invoice) can be changed in the Business Setup -> Your Clinic -> Invoice Settings.

Click on the dropdown list option for the "Invoice Template" and "Public Invoice Template" fields to change the invoice style, as desired.