Post Purchase Upsell shows an additional offer on the order confirmation page after payment, before the thank you screen. The shopper can add the item with one click and it is appended to the original order. No second checkout, no second shipping fee.
Offers can be driven by AI recommendations based on what the shopper just bought, or fully refined to your rules if you know your catalog better than the model. Most merchants use a mix: AI for broad catalogs, hand built conditional logic for narrow ones (for example "show insoles only to shoppers who bought shoes" or "show subscription upgrade only on first time orders").
