How can I ensure that BUSY generates an e-invoice automatically when I save a vendor bill?

To ensure that BUSY generates an e-invoice automatically when you save bill you need to enable E invoice option in BUSY and to enable e invoice in BUSY you can follow some steps: 
 Step 1: Go to Administration and then click on Configuration option. 
 Step 2: Now click on Feature and option and then click on GST and VAT option 
 Step 3: Enable E-Invoice Required option by specify yes and click on configure 
 Step 4: Now specify From Place and pincode. 
 Step 5: Enable other options as per Required Now click on OK option and then 
 Click on GSP Configuration. 
 Step 6: If you did not create GSP Yet then go to E-Way bill portal 
 Step 7: Login the E way Bill Portal and go to Home 
 Step 8: Click on Registration and then Click on GSP 
 Step 9: After Click on GSP Registration Send the OTP 
 Step 10: Enter the OTP and verify the OTP 
 Step 11: Click on Add New Option And select the GSP name and 
 those are Webtel electrosoft PVT. LTD. And Pinnacle Finserv Advisors 
 Pvt. Ltd. 
 Step 12: After Select One of the GSP'S Create User name and password and save. 
 Step 13: After create GSP Go to Administration and then on Configuration and 
 Fearure and option and then click on GST VAT 
 Step 14: In GSP Configuration enter GSP ID's and then save the configuration. 
 Step 15: Now Go to administration and then click on configuration. 
 Step 16: Now click on Voucher series configuration and select the sale Voucher type and then click on voucher series 
 Step 17: After click on voucher series click on voucher configuration and enable Generate E-Invoice after saving voucher and save the configuration. 
 Step 18: Now Go to transaction and select voucher type and then Click on Add option. 
 Step 19: Enter all the required details in their respective feilds in voucher 
 for instance date. party name etc. and save the voucher and it will 
 show you the prompt for Genterate E-Invoice you need click on Yes. 
 Stpe 20: Now you can click on Automatic option and check possible error and rectify 
 them and then click on view and generate and check all details and You 
 can generate E-Invoice and then can print it.