If nothing was unclear or difficult, say so. Skip questions about steps you did not experience; use not applicable where appropriate.

Which checkout step was hardest to complete?
Was any cost or requirement unexpected?
What information would have helped earlier?
Was the payment step clear without revealing card details?
What should be explained before you begin checkout?

Author notes / illustrative keys where applicable:
1. Locate the checkout step that created the greatest difficulty so investigation has a concrete target. Separate form, payment and information problems before redesigning the whole journey.
2. Identify a cost or requirement disclosed after customers expected it to be settled. Clarify the actual terms earlier without assuming every unexpected charge was improper.
3. Find information that would have enabled preparation before the difficult step. Move the explanation to its decision point rather than add a longer final confirmation.
4. Check whether payment instructions and confirmation were understandable, excluding card numbers and other secrets. Investigate reported confusion separately from whether the transaction actually succeeded.
5. Identify prerequisites customers need before entering checkout, such as accepted arrangements or verified charges. Explain them accurately without treating survey answers as transaction authorization.