When to send it
Send this one to two days after a free trial expires without a payment. Wait longer and the details fade; send it the day the trial ends and it feels like a sales chase. A plain email from the founder's own address, with one sentence and the link, tends to get more replies than a designed newsletter. A single reminder a week later is reasonable. Anything beyond that turns a question into pressure.
Why these questions
People who let a trial lapse fall into very different groups, and the first question sorts them: those who barely started, those who dabbled, and those who used it properly and still said no. Each group needs a different fix. The first is an activation problem; the last is a product or price problem.
The reason question is deliberately blunt, with the usual causes as options, including "I'm still deciding" and "I only wanted to look around". Those two matter. They separate people you could still win from people who were never going to buy, so you don't spend effort chasing the wrong group.
Three of the reasons open a follow-up. If the product didn't do what they needed, they describe what they hoped it would do. If the price was the problem, they choose what would have suited them better: a smaller plan, monthly billing, a longer trial or a lower first payment. Nothing asks about their budget or income. If they picked a competitor, they name it.
Everyone finishes with one open question: what single change would have made them upgrade. Undecided people then see a closing note that there's no rush.
The coupon
Twenty percent off the first three months gives anyone on the fence a reason to come back now, without training customers to expect a permanent discount. Unique codes keep it to the person you emailed. Every customer who finishes sees it, including those who said they were only browsing.
What to do with the answers
Split the answers by the first question before reading anything else. If most people barely used the product, put your effort into the first days of the trial; the onboarding survey will show where they stalled. If heavy users still left, read their "what did you need" and price answers closely, since those people understood the product and decided against it.
Watch trial length too. If "I didn't have time to try it properly" keeps appearing, a longer trial or an easy extension may convert better than any discount. Compare these answers with cancellation reasons from paying customers: problems that show up in both lists deserve the top of your roadmap.