> For the complete documentation index, see [llms.txt](https://docs.ngsurvey.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ngsurvey.com/form-management/security/security-items/invitation-code.md).

# Invitation Code

## 📧 What is an invitation code ?

The invitation code security item will check for the invitation code that was sent to the respondent using the [email](/form-management/campaigns/campaign/email-distribution.md) or [sms](/form-management/campaigns/campaign/phone-sms-distribution.md) campaigns. 

{% hint style="warning" %}
Codes generated during [campaigns](/form-management/campaigns.md) can only be used once to take a survey.
{% endhint %}

## 🔅Password properties

* **`Only invited recipient can particpate`** you can open your survey to respondents who didn't not receive any invitation code or only to respondents having a valid invitation code from a [campaign](/form-management/campaigns.md). Note that if this option is un-selected respondent without code will be able to take the survey multiple times while respondent having a valid invitation code will only be able to submit once their answers.

{% hint style="success" %}
This security item can be used as a [key provider](/form-management/security/key-provider-concepts.md).
{% endhint %}


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.ngsurvey.com/form-management/security/security-items/invitation-code.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.