You may record partial payments on invoices.
For example, you issue an invoice for $500.00, but the customer only sends you $250.00 and begs for more time. With this feature you can record the partial payment and issue a new invoice which reflects the payment and balance due.
Note that you can also use this to show down payments already received on acknowledgements, the value of something to be traded on a proposal, etc.
If partial payments are recorded, the totals shown are adjusted accordingly: