# How to Restrict user from checkout?🤔
**Objective: Blocks checkout for customers tagged “banned” and displays a custom validation error..**
### **Step 1: Create the Function**
* Navigate to the **Nexus Dashboard** and click **Create Function.**
* Select **Validation Functions** from the list.
### **Step 2: Choose Validation Type**
* Click on **Conditional Cart & Checkout Validation.**
* A **setup screen** will appear.
### **Step 3: Configure Basic Settings**
* Enter the **Function Name.**
* Select the **Function Input Type** to **Advanced Input.**
* Select **Customer Tags** from **Customer Qualifier.**
* **Condition:** Does Match one of the
* **Customer Tags:** Banned
**Note:(Validation Message will be shown Only Banned -tagged customers …You can assign the Banned tag to a customer by adding it directly to their profile.)**
### **Step 4: Add a Validation Error**
* Click on **Add Validation Error** to begin setting up your **validation rule.**
* A **popup** will appear.
### **Step 5: Define the Validation Details**
* **Select the User Journey:** Choose the page where the **error** should appear (e.g., **Cart or Checkout**).
* **Select the Target:** Define the **specific field or section** (e.g., Email)
* **Enter the Error Message:** This is the **message customers** will see when **validation fails.** And **Click on Save.**
### Step 6: Configure Validation Settings
To ensure your **function works** correctly and is enforced during **checkout:**
* **Scroll down** to the **Validation Settings** section.
* Check the box **labeled Active** to enable the **validation function.**
* Check **Block on failure** if you want the **checkout to stop** when the conditions of your **function are not met** (e.g., if the required **bundle items** aren't in the **cart**).
* Once **everything is set,** click **Save** to create your **validation function.**
**🎉 You're all set!** Enjoy a **smarter, smoother checkout experience** with **Nexus Function. 😊**
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