To cancel an event make sure that your are no longer selling any tickets / products. You can do this by changing the event sales end date so that it's in the past. *
You can then contact all of your customers by clicking "Email" from your event management menu:
This will allow you to send an email to all customers informing them that the event has been cancelled.
If you need to make refunds you can do this via your PTA Events website for entire orders OR through your Stripe dashboard for partial refunds. To find all the orders placed for this event click "Orders" from your event management menu:
Alternatively click the order value in your event admin listings:
For more information on processing refunds, please see the following FAQ:
* This assumes that you haven't overridden the event sales end date by setting sales dates for your tickets / products.