The existing built in reports can only be customized by their edit screen as Tut describes above however you can also
-
copy the report to a spread sheet program (via the “Copy to clip board” button or selecting the text in the report directly) and enhance it there
-
"Custom Reports can be used to build reports with some similar features. See Create custom reports
-
Currently for specific reports, “Report transformation” provide much greater control.
-
Managers API can be used for more elaborate tasks if you have access to the programming skills
For localisation examples:
-
Tax summary can be customized via a “Report transformation” of type “Tax summary” See Localisation: GST/VAT worksheet programming guide
-
Similarly the “Taxable Purchases per Supplier” report can be customized via a “Report transformation” of type “Taxable Purchases per Supplier” see this localisation example