@Samantha73
1. the language setting in customer card is blank
2. User setting means "My Setting"?
3. GL setup means VAT settings in GL? We were using Normal VAT, now I changed to Sales Tax. Does it help?
4. Did you mean to change the invoice header from the source? Could you provide some screen capture?
"Once the invoice is created with an incorrect setting it cannot be changed so perhaps if the above do not work, and all your customers in AU, you can hard code"-----Did you mean create a new invoice? I did. It did not work. The company is located in Singapore.