Specific patient set-up

Open the patient data panel. Next, go to [Preferences].
Under the [Personalised pricing] option, click [Apply 3rd payer payment scheme by default].
After this, the rates for this patient will always be set to the 3rd payer rate.

Setting up all patients

Open the [Settings]. Choose for [Patient] > [General].
Tick
[Apply 3rd payer payment scheme by default].
Every patient is now charged at 3rd payer rate unless for specific patients where it is set differently at the patient level.