# Do not allow Modification of Retrieved Challan
**YouTube:** [How to Restrict Modification of Retrieved Sale Challans?](https://www.youtube.com/watch?v=SV1TT43u7po\&t=12s)
## How to Restrict Modification of Retrieved Sale Challans?
In this tutorial, we will learn how to **restrict the modification of a retrieved Sale Challan** in Logic ERP. This setting ensures data consistency by preventing edits to challans already used in billing.
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### **Access Sale Voucher Configuration**
* Navigate to **Sale Voucher Configuration** in Logic ERP.
* Select the **relevant Challan Series** for which you want to enable this feature.
* Locate the option labeled as: **“Do not allow Modification of Retrieved Challan”**
* **Keep this feature disabled** initially to observe the default behavior.
***
### Implement Feature as Disabled
* Create and **save a Sale Challan**.
* Open the **Sale Bill** window.
* Use the **Retrieve Challan** option and select the item to retrieve into the bill.
* Save the **Sale Bill**.
Now go back to the **Sale Challan** window.
* Attempt to **modify the same challan** (e.g., change the quantity).
* Save the challan.
Since the restriction was **disabled**, the system **allows modifications** even after the challan has been retrieved in the bill.
***
### Implement Feature as Enabled
* Return to **Sale Voucher Configuration**.
* **Enable** the option:
> **"Do not allow modification of Retrieve Challan"**
* Save the settings and restart the software if needed.
* Again, try to modify the same Sale Challan that was retrieved in the bill.
* Change the quantity and attempt to save.
This time, the system will **prevent the modification** and show an error message:
> **"This Challan has already been retrieved in a Sale Bill. Modification is not allowed."**
***
### Summary
| Setting | Behavior |
| ---------- | ------------------------------------------------- |
| ❌ Disabled | Allows modifying retrieved challans |
| ✅ Enabled | Prevents editing challans already used in billing |
This feature is crucial for ensuring data integrity between your **challans and sale bills**.
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