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==================Hi everyone,I’ve built an anonymous survey and would like to offer participants a €5 voucher as a thank-you. To do that, I need to collect their email addresses – but these must be stored separately so they can’t be linked back to the survey responses.What I’ve tried so far:
At the end of the survey, I added a link to a second survey where participants can leave just their email. The issue: that link can be copied and shared with friends, meaning I might end up sending vouchers to people who never actually completed the original survey.My question:
How can I set this up so that

1. emails are truly stored separately from survey data, and
2. only actual participants are able to submit their email?

Has anyone implemented something like this before or found a practical workaround?Thanks a lot! 🙏

Hi, you can put the link to the second survey in the End-URL of the first survey and set the End-URL to load automatically in the survey settings under "Presentation" Strictly speaking, it's still possible then to share the link, but I think it's rather unlikely that someone does it.

The End-URL-to-a-second-survey approach is the right shape, and the flaw you spotted is real — that second survey's link, once visible, can be copied and shared, so "did this person actually complete survey #1" and "did this person just have the link" become indistinguishable. Worth being precise about why, because the fix is a small addition to what you already have, not a different approach.

The missing piece is a token that can only be produced by actually finishing the first survey — and LimeSurvey already generates one for you on every single response, token-based or fully anonymous: {SAVEDID}. Pass that along as a parameter on your End URL redirect, and on the receiving end, the very first time a given {SAVEDID} shows up, record which email claimed it. Any later hit carrying that same {SAVEDID} but a different email gets rejected outright. Someone can still share the raw URL, but the moment the real participant uses it once, the link is "spent" for anyone else — a genuinely new claim now requires a genuinely new {SAVEDID}, which only comes from actually completing the survey again.

As a second layer, a simple IP-based check helps too: one IP submitting several different reward emails in a short window is a strong abuse signal on its own.

I built exactly this (End-URL → automatic voucher/gift-card email, with the {SAVEDID}-binding baked in so this exact loophole is closed) after hitting the same issue running my own group's studies — REWARDR, ersan.eu/qr-sistem/, happy to answer anything if it's useful for your setup.