# Control Rate Updates for Transacted Lots in Purchase Voucher
**YouTube:** [Why Rates Are Not Updated in the Lot Master After Retrieving a Purchase Challan?](https://www.youtube.com/watch?v=PH2l2e6XA04)
## Why Rates Are Not Updated in the Lot Master After Retrieving a Purchase Challan?
This tutorial explains **how to control the behavior of rate updates for transacted lots when retrieving a Purchase Challan into a Purchase Voucher**, and how to adjust the system setting to allow or restrict such updates.
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### Retrieve Purchase Challan in Purchase Voucher
Begin by creating a Purchase Voucher entry.
**Steps:**
* Open the **Purchase Voucher** window
* Start a **new entry**
* Retrieve the **Purchase Challan**
Once the challan is retrieved:
* The **rates defined in the challan** will automatically be fetched into the voucher.
* **Save the voucher entry**
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### Check Rate Behavior in Modify Mode
Reopen the **Purchase Voucher in Modify Mode**
You will notice:
* **Rates of most items get updated automatically**
* This happens due to **user-defined purchase rate formulas configured in the system**
However:
* **Some items may not have their rates updated.**
* Press **F5 on the Lot** to check the **lot details and rate information**.
* You will observe that the **rate for that specific lot remains unchanged**.
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### Identify the Reason Using Stock Query Report
To understand why the rate did not update, analyze the stock movement.
**Open the report**
* Go to **Stock Query – New Report**
Generate the report for **only the items included in the challan**.
In the report you will see:
* **Purchase Challan created on 18th December** → Stock added
* **Sales Bills generated on 09th March** → Some items sold
**Key Observation**
* Items **already used in sales transactions** did **not update their rates** when the purchase voucher was modified.
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### Why This Happens
* This behavior occurs because of a **system setting enabled in the Logic Admin Panel**.
* The setting prevents **rate changes for lots that have already been transacted**.
**Change the System Setting**
To allow rate updates for such lots:
**Follow this path**
* Open **Logic Admin Panel**
* Go to **Global Settings**
* Navigate to **Purchase Options**
* Locate and **untick the option**
> **“Do not allow change in rates of transacted lots.”**
* Save the settings and **Restart the software.**
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## Repeat the Process for Testing
To clearly understand the behavior, repeat the process.
#### Create Purchase Challan
* Create a **Purchase Challan**
* Enter item details and **save the challan**
#### Generate Sales Transaction
* Create a **Sales Bill**
* Sell **one or two items from the challan**
* Save the sales bill
This ensures those items become **transacted lots**.
#### Retrieve Challan in Purchase Voucher
* Open the **Purchase Voucher window**
* Retrieve the **same purchase challan**
* Save the voucher
#### Open Voucher in Modify Mode
* Now Re-Open the voucher in **Modify Mode**.
**This time you will notice:**
* Rates of all items, Including the transacted lots are updated automatically according to the user-defined purchase rate formula.
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### Practical Approaches to Handle This Scenario
There are **two practical ways** to manage rate updates effectively.
#### Approach 1: Disable the Restriction Setting
* Disable the option **“Do not allow change in rates of transacted lots”**
* This allows **automatic rate updates even for transacted lots**
#### Approach 2: Apply Rate Formula in Purchase Challan
* Instead of applying the formula in the **Purchase Voucher**, apply it directly in the **Purchase Challan**.
Benefits:
* Rates are **calculated and saved at the challan stage**
* When the challan is retrieved into the purchase voucher:
* The system **uses the same predefined rates**
* Even if the lots have **already been transacted**
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### Conclusion
By controlling the **rate update settings for transacted lots**, businesses can:
* Maintain **accurate purchase costing**
* Avoid **unexpected rate changes**
* Ensure **consistent stock valuation**
* Manage **purchase formulas effectively**
This feature provides **flexibility in handling purchase transactions while maintaining data accuracy**.
