# 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](https://docs.ngsurvey.com/form-management/campaigns/campaign/email-distribution) or [sms](https://docs.ngsurvey.com/form-management/campaigns/campaign/phone-sms-distribution) campaigns. 

{% hint style="warning" %}
Codes generated during [campaigns](https://docs.ngsurvey.com/form-management/campaigns) 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](https://docs.ngsurvey.com/form-management/campaigns). 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](https://docs.ngsurvey.com/form-management/security/key-provider-concepts).
{% endhint %}