When to send it
Email it the day after the final session, or along with certificates or recordings. Students are at their most reflective right at the end, and the testimonial question works best while the feeling of having finished something is still fresh. Add each student's first name to the link as ?name= and the survey opens with a personal greeting.
Why these questions
The first page is about the course. Overall satisfaction on the five-point CSAT scale gives a figure you can track from one cohort to the next. The second question asks whether the course helped the student reach the goal they started with, which is the outcome that brings people back for another course. Anyone who answers "partly" or "not really" is asked what was missing. Then comes the familiar 0 to 10 question about recommending the course to a friend, the Net Promoter question.
The second page asks the student to describe the course in a sentence or two, as they would to a friend. That framing draws out natural, specific language rather than generic praise. Straight after it comes a separate consent question: may you use what they wrote as a testimonial, with their first name, without their name, or not at all.
Testimonial consent and the coupon
Keep these two apart, and tell students you have. The consent question's description says the coupon is the same whichever option they pick, and the survey issues the code to everyone who finishes, including people who say no or leave the testimonial blank. That keeps the testimonials honest and the consent freely given. The survey has two end screens, one thanking students who agreed to share their words, and both show the same coupon.
Advertising rules in several markets expect you to be open about incentives connected to testimonials. A short line near the quotes, saying that students who complete your feedback survey receive a discount on a future course, is a simple precaution.
The coupon is a unique 20% code for the next course. It is generous on purpose: someone who has just finished one course with you is the person most likely to take the next, and a unique code keeps the discount from spreading beyond them.
What to do with the answers
Export the answers where consent is a yes and keep them with the date and the name option the student chose, so you can always show where a quote came from. Before publishing, check each quote still reads well on its own. Read the "what was missing" answers before planning the next cohort, and compare them with the course mid-point check-in from the same group.