How to enable the Specify Serial Numbers option

In order to have the Specify Serial Numbers option available on a Purchase Order, it is necessary to:
Enable the Serial Numbers on the stocked part in question by following these steps:
1. Go to Stock
2. Click on Stocked Parts Menu
3. Open Stocked Part Maintenance
4. Select the stocked part in question and click on Summary
5. Enter modify mode (CTRL+M) and tick the Serial No's box
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Then, you will need to reserve them on the Works Order. This can be done from:
1. Go to Production
2. Click on Works Order Enquiry
3. Navigate to the works order and click on Serial Numbers at the bottom
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After completing these steps, you may raise a Purchase Order and the option is now available.