How do I force the sale of a product if another is in the basket?

This option can be used, for example, when you are selling a child ticket that needs to have an adult ticket purchased with it.

To include a product, head to "Admin" > "Events" and then select "Tickets/Products" from the "Manage" menu of the relevant event:

Then select "Add Product" from the product management menu:

Enter the product details and then select the dependent product from the dropdown list in the "Dependent Product" field:

You will be able to view in your Shop/Events page if a product has a dependency:

And although the ticket can be added to the basket, you will not be able to proceed through the checkout process without including the dependent product: