We have now added the ability to have our discount engine look at historical invoices to decide if the customer should get the discount or not. We commonly see this functionality used for people that want to provide sibling discounts for the kids that sign up during the same season.
First you will need to create or adjust a Discount Code. Check out our Help Center article if you need to learn how to do this here.
There is a check box under the Options section of the Discount Setup to look at prior invoices as far back as 2 years. Once this is activated, the Required Quantity, Max in Cart, and Sequential Camp Discount can no longer be used for this Discount Code.
How it Works
If a customer has an invoice in the past that qualifies them to now receive a discount, when the new item is added to the cart the discount will appear automatically (if it is set as automatic). Here is an example of a prior registration invoice where the customer registered one child and later registered the second child to receive the "Add On Sibling Discount".
The ideal situation would be to select one of the following on your discount setup to ensure the past invoice would not be dated back too far (Same Season or Same Team) otherwise you risk the possibility of giving away unintentional discounts.