How can I group certain invoices together for my client?

By default, all assignments go onto one invoice. However, you can set assignments to be grouped together on invoices by purchase orders. Go to Client > Edit Client > Group by PO toggle. Then add a unique purchase order to all the assignments you want grouped together. For instance, if you have 3 assignments but you want 2 grouped together since they are for “night shift” jobs. Go to each of those assignments, add the purchase order “night shift” to the assignment under Edit Assignment. On invoices, both assignments that have the “night shift” PO will be on one invoice, an the other assignment with be on the other invoice.