When to send it
Most stores already send an abandoned checkout email. It usually says you left something behind and shows the cart. Add this survey link to that email, below the button back to the cart. Shoppers who were simply interrupted will click through and buy. The ones who left for a reason now have a quick way to tell you what it was. Shopify lets you edit the abandoned checkout notification under Settings, then Notifications, and other platforms have a similar template.
Send it within a day. After that, many shoppers can't recall which store they were on, let alone why they left.
Why these questions
The survey is four questions, because these shoppers owe you nothing and haven't paid. The first asks what stopped them from finishing, with one answer: delivery cost or time, a higher total than expected, browsing, comparing shops, not wanting an account, a confusing or broken checkout, a failed payment, doubts about size or fit, or something else. Published checkout research keeps pointing to surprise costs and forced account creation, which is why both are on the list.
Shoppers who pick a broken checkout, a failed payment or something else are asked what happened, including which step and which device. Those answers are bug reports. A payment method that fails on one phone browser can quietly cost you sales for weeks before anyone notices.
Everyone is then asked whether anything was missing that would have helped them decide: more photos, clearer delivery dates, a size chart, a returns policy. The last question asks how likely they are to come back and finish the order, which helps you judge whether a reminder is worth sending.
The coupon
The reward is free shipping with a shared code that expires after 48 hours. Delivery cost is a frequent reason to leave a cart, so the coupon answers the most likely objection head-on. The short expiry keeps it a one-time nudge instead of a reason to abandon every cart in the hope of a code. Every shopper who finishes the survey sees it, whatever they chose. If shipping is already free in your store, switch the reward to a small percentage instead.
What to do with the answers
Count the reasons every week for the first month, then monthly. If cost surprises lead, show delivery charges on the product page rather than at the last step. If browsing and comparing lead, your checkout is probably fine and your follow-up emails matter more than fixes. Pass every checkout and payment report to whoever runs your store setup the same day, with the device details.
For a wider look at the whole site, try the online store experience template. To measure how much effort checkout takes for customers who did buy, use customer effort for checkout and returns.