I need to split or divide one large invoice containing many line items in the accounting software. What is the process for doing it?

To split voucher you need to follow some steps: 
 Step 1: Go to Administartion and then click on Configuration. 
 Step 2: Now click on Voucher series configuration and then click on voucher type that you want to split. 
 Step 3: Now click on series of that voucher type and then click on Voucher configuration. 
 Step 4: Now press short cut key CTRL+SHIFT+ALT+X and one window will be prompt for split voucher. 
 Step 5: Now select option for Split voucher After Saving. 
 Step 6: Now select the option split voucher Before printing or After printing. 
 Step 7: Now select option for the Action to be taken as split Items or Change voucher Amount.If you select voucher amount then target voucher will be Journal voucher but if you select item Then it will post voucher type that you selected. 
 Step 8: If you select option for Split item then it will show you options for item to be splitted,you need to select basis on which you want to split voucher. 
 Step 9: Now specify the date to be posted in Target voucher and also enable prompt for spliting and other options as per your requirement. 
 Step 10: Now click on OK option and save the configuration. 
 Step 11: Now go to the Transaction and then enter your voucher during saving it will show you the prompt for split voucher and you can split your voucher by click on Yes Option.