1. Go to File -> System option -> General tab -> At sales posting account method -> tick Customer Sales Type.
2. Go to Debtor -> Sales Type -> Key in the information (eg: sales type : LOCAL , sales Acc: Sales-software. -> Save.
3. Go to Debtor -> Debtor Maintenance -> There is one field called: sales type -> browse to choose.
4. Go to Sales invoice -> Will have one field sales type -> Call debtor -> Will show sales type from previous setup at debtor maintenance.
5. When save the transaction. Posting account code will follow the sales type setting.