When you create a new company in the BUSY, you will find an option for enabling GST/VAT in the GST/VAT information section. You can enable GST here and fill in the related information,but If you have not enabled it here and have already created the company, but now wants to enable it,so you can follow given steps:
Step 1:Go to the Administrtaion menu,
Step 2:Click configuration,
Step 3:Click Features and Options,
Step 4:Click GST/VAT Tab,
Step 5:Here you can select type GST,Type of Dealer as reguler,GSTIN number and click Create Default GST Masters,define tax rate as you want, then create.
Now you can bill anything related to GST in BUSY.