When there is a temporarily stop of business with a customer, you can block new orders to be created for this customer. You can have the options of blocking all the work flow or let the delivery and billing to continue for any open orders.
VD05 - Block/Unblock Customer
OVAS - Sales Order Type Blocking reasons
OVAL - Blocking reasons links with Sales Order Type
OVZ7 - Delivery Blocking reasons
OVV3 - Billing Blocking reasons
In 4.6x, if you found that your Sales Order Billing Block is not working, it is because you need to build the Billing Block for the Billing Type.
SM30 - Table/View V_TVFSP