Smokeball automatically sets your client as the debtor on invoices, however sometimes you may need to invoice someone different. This is how you set a different debtor on a matter:
In Smokeball WebApp
From the matter, select Edit Matter
From the Edit Matter screen, click in the Debtors field where you can type to search and select an existing contact. Otherwise at the bottom of this dropdown menu you will see +Add New Contact if they are not already in your system.
In Smokeball Desktop
From the matter, Open Info and select the Billing tab where you can enter Debtors