If you have several unpaid invoices for the same customer and want to merge them into one large invoice, you can do so from a customer's page. Doing this will move all invoice line items and attachments into one invoice; the other invoices will then be deleted.
Merge Customer Invoices
1. Open the Customer page related to the invoices you want to merge.
2. Scroll to the Invoices section, and then the Unpaid Invoices section.
3. Check the box next to each invoice you want to merge, and then click Merge Selected Invoices.
4. A confirmation popup appears, explaining how these invoices will be merged into one. Click OK to continue.
A message appears at the top of this customer's page, confirming that the invoices were successfully merged.