In Tally, exactly as you normally would, with two additions.
1. Type `/hidden` anywhere in the editor to insert a **Hidden field** block, and name the field `vypw`, in lower case. This is where each respondent's password arrives from their link. Tally's [hidden fields](https://tally.so/help/hidden-fields) are case sensitive, so the spelling has to match exactly.
2. Add a **Short answer** question called **Verification code** as the first question, and mark it **Required**. Underneath it, write something like "Filled in automatically, please leave this alone."
3. Click the handle to the left of that question, switch on **Default answer**, and pick the `vypw` hidden field from the dropdown. This is the step that makes the whole thing invisible: the password fills the box on its own, and a verified respondent types nothing.
4. Put a **page break** straight after it, so the code box is alone on page one and your questions start on page two. Tally only acts on a page jump when somebody presses Next, so the screen-out in the next step will not fire unless the code box has a page of its own.
5. At the end of the form, add two **thank you** pages: first the one people see when they finish, then a second one saying they need to start from their invitation link. Order matters, the first thank you page is where a normal finisher lands.
6. Click **Publish**.
The visible question is doing real work. A hidden field on its own can be left empty by anyone who opens your form directly, and Tally will accept that submission, and the next one, and the one after that. A required question cannot be left empty.
You now have: a form whose first question is a code box that fills itself in.
Two settings, both free, both in your published form.
1. On the **Verification code** question, add conditional logic: **if** the answer **does not start with** `vyp_`, **jump to** the second thank you page, the one about starting from the invitation link. Anyone who wandered in without a password stops there instead of filling in your study.
2. In **Settings**, under **Access**, turn on **Prevent duplicate submissions** and choose the **Verification code** question as the unique identifier. Not IP address and not Respondent ID: those can be worked around by switching network or browser.
Tally's [duplicate rule](https://tally.so/help/prevent-duplicate-submissions) now runs on their servers before a response is stored, so Tally turns away a second attempt carrying a spent password with "Form submission not accepted. It looks like you have already filled out this form." What it does not do is check that a password came from us, because Tally has no way to know what your passwords are. That is the next two steps.
One thing to expect in your results: somebody who is screened out here still leaves a row, carrying whatever they typed in the code box and none of your survey answers. It is removed in step four, and until then it is obvious what it is.
You now have: a form that accepts each password exactly once and turns away anything that is not shaped like one.
In your [VerifyYou dashboard](https://platform.verifyyou.com/dashboard/verifications), open a verification and go to the **Integration** tab.
1. Make sure the method is **One-time passwords**. If it is set to something else, click **Switch method** and choose it.
2. Set **how many one-time passwords** you need. Ask for at least twenty percent more than the respondents you expect. Passwords cost nothing, and running out mid-study screens out real people.
3. Send us your Tally form link. We give you back a **gate link** for this study. That is where we hand a verified respondent their password.
4. Set the destination for verified people to that **gate link**.
You now have: your study link, which is the one you share, and a gate link doing the handover.
In your published form's **Integrations** tab.
1. Find **Webhooks** and click **Connect**.
2. Paste the **endpoint URL** we gave you with your gate link.
3. Paste the **signing secret** we gave you alongside it. That secret is how the endpoint knows a submission really came from your form.
4. Save.
Tally now tells us about every submission as it lands, and this is the step that checks a password against the ones we actually issued. A submission carrying a real, unused password is left alone. One carrying a password we never issued is removed from your results, and so is one that arrived with no password at all. [Webhooks](https://tally.so/help/webhooks) are free on every Tally plan.
You now have: a study where a response has to arrive with a password we issued in order to stay in your results.
The link you hand out is the **study link from VerifyYou** (the `app.verifyyou.com/verification/...` one, from **Copy** in the dashboard), never your Tally link. This is the whole point: the VerifyYou link sends every respondent through the face check first, then redirects the verified ones into your Tally form with their one-time password already attached. Anyone who opens the raw Tally link skips the check, so only ever share the VerifyYou link, in your panel, your sample provider, or your invite email.
You now have: a fielded study where everyone who reaches your questions came through the check. That's the whole setup.
## Two settings worth leaving alone
Keep **partial submissions** off, so an abandoned attempt does not sit in your results looking like a response. And if you know the size of your sample, set a **submission limit** to match the number of passwords you asked for, so a study that has finished closes itself rather than collecting stragglers.
## When something looks wrong