To put a Customer on Stop Credit, go to the Customers tab in the navigation sidebar and select the customer from the list. Go to the Terms / Pricing tab and select Edit. Select the Stop Credit option and select Save.
The toolbar updates to reflect the customer is now on Stop Credit.
When you return to the Customers list, the account is highlighted in red. This is done for all accounts on stop credit and gives an easy way of recognizing accounts of this type.