When processing a transaction assigned to a customer who already has a live Customer Rewards account, you may wish to block Rewards points from being earned on that particular transaction.
When in POS, with the items added to the transaction and the customer assigned, you will see the Customer Rewards function present in the upper menu:
Click the button marked Customer Rewards and you will be taken to the options screen that will allow you to block points accrual:
Click Add NOPOINTS Item, and this will return you to POS, from where you can then process the transaction as per normal.
No Customer Rewards points will be earned on this transaction, regardless of whether or not any items included in the purchase would normally result in points being earned.