There may be cases where your Event doesn't have a billing contact. If this is true, you'll see something like this when looking at your Event Overview page:
Notice the Blue Button labeled Configure Billing Contact. This button will guide you to our Event Billing Settings Page. Here you can configure a Billing Contact.
What is a Billing Contact? This person is responsible for all charges associated with this Event. This person will be sent both Pre-Paid and Post-Paid invoices generated for this Event.
To configure the Billing Contact for this Event, click on the dropdown highlighted in the image above. You should see a list of users associated with your account. Pick the appropriate user here and click the Save Changes button to persist your choice.
After this is complete, you can now Add a Payment Method to your Event!