You may change the Debtor group 1 and / or 2  for selected debtor (customer / client) account(s). TurboCASH4 - Debtor accounts - Change groups

To change the Debtor group 1 or Debtor group 2: 

1.On the Edit → Debtors ("Debtor accounts" screen) select the Debtor(s), right-click on Debtor group 1 or Debtor group 2 context-menu. 

If you need to select multiple debtor accounts, press the Ctrl key and click on each debtor account.

2.Select "Empty" or the available Debtor group from the sub-menu. The Debtor group 1 or 2 will change on the reports.