I want to setup a recurring invoice for a client. How do I create recurring invoices in this system?

In order to create a reccuring invoice for a client you have tp use voucher replication feature , you can follow these steps below:
Step 1: First post one voucher with all deatils for which you want to replicate.
Step 2: Go to administration
Step 3: Then go to bulk updation and select option voucher replication.
Step 4: Select option single voucher in diff dates.
Step 5: Then select voucher type of the voucher you want to replicate.
Step 6: Click on new template
Step 7: Then select voucher type and select date range .click on show voucher list.
Step 8: Click on show voucher list and select the voucher.
Step 9: Mention a template name .
Step 10: Select then template for replicate voucher and select basis for voucher to replicate ( daily , weekly , fortnight or monthly ) as per you requirement 
Step 11: Mention starting and ending date that will be considered to replicate voucher 
Step 12: Then select days between which voucher will be posted .
Step 13: Then mention yes in option for generate amount randomly if you want the amount of all replicated voucher to be different and mention range of amount and mention no in generate amount randomly if you want same amount for all voucher .
Step 14: Select list of holidays to skip port voucher on holiday 
Step 15: Lastly mention number of copies to post and click on replicate.
By following these steps, you can replicate voucher in BUSY.