If you have a client whose uses insurance to pay for some sessions, but pay out-of-pocket for other sessions, you still want to set the client’s overall billing type to Insurance on the client's Billing & Insurance tab.
For any client who’s insurance company will pay you, set her billing type to Insurance. You can read more about it here: Setting up billing for an insurance client.
Once you’ve changed the client’s billing type, all future recurring sessions will automatically update to reflect the new billing type.
Now that you’ve changed the client’s overall billing type, schedule all the client’s sessions as you normally would. When a session comes along where the client is responsible for 100% of the fee, change that individual session’s billing type to Self-Pay.
You can read more about changing the billing type for an individual session here: Changing the Billing Type, Co-Pay, or Cash Write-off at the Session Level.
When you change the individual session’s billing type to Self-Pay, the total fee for that session will be applied to the client’s balance. No portion of the fee from that session will be applied to the client’s insurance provider’s balance.