# Validate Credit Card Number Length to 16 Characters
**YouTube:** [How to Enforce 16 Character Credit Card Number Validation in Sale Bill?](https://www.youtube.com/watch?v=KcMcBn--BwY)
## How to Enforce 16 Character Credit Card Number Validation in Sale Bill?
This tutorial will guide you through the process of enabling a feature in Logic ERP that **validates credit card numbers to ensure they are exactly 16 characters long** during billing.
***
### Access Global Settings in Logic Admin
* Open **Logic Admin**.
* Navigate to **Global Settings**.
* Under **POS Options**, go to the **POS Options 1** section.
* Locate and enable the option labeled as:
> **"Validate Credit Card Number Length to 16 Characters"**
* Click **Save and** **restart the software** to apply the changes.
***
### Implement **the Feature in the Billing Window**
* Open the **Sale Voucher** window.
* Start a **new transaction** and add items to the bill.
* Click **Save** to proceed to the **payment window**.
* Select **Credit Card** as the payment method.
***
#### **Test Case 1: Enter Invalid Credit Card Number**
* Enter a **credit card number that is not 16 digits long**.
* Attempt to save the transaction.
* Result:
* An **error message** will appear:
> “Credit card number must be 16 characters long.”
* The system will **not allow the transaction** to proceed.
***
#### **Test Case 2: Enter Valid Credit Card Number**
* Now, enter a **valid 16-digit credit card number**.
* Save the transaction.
* Result:
* ✔️ The payment will be **successfully accepted**.
* No error is displayed.
* The system confirms that the **validation is working correctly**.
***
#### **Why Use This Feature?**
* Ensures **accuracy** and **standard compliance** for credit card entries.
* Prevents **incomplete or incorrect card data** from being processed.
* Enhances **billing integrity** and **reduces transaction errors**.
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