It's great to have you here, @Mr Milton.

Yes, you can choose the option Autofill from existing inventory when creating the sales order. By doing this, you'll have the same serial number for both inventory assembly item and the sales order items.

Let's first check your QuickBooks preferences to ensure that the serial number feature is enabled.

1. Go to the File menu.
2. Choose Preferences.
3. Select the Items & Inventory.
4. From the Company Preferences tab, click the Advanced Inventory Settings button.
5. Pick the Serial/Lot Numbers tab.
6. Make sure to mark the Enable Lt or Serial Numbers tick box.
7. Choose the Serial Numbers radio button.
8. Mark the specific forms where you want the serial number to be added.
   • You can also set default settings for your inventory and assembly items.
9. Click Ok.

Once completed, the serial number tracking is enabled for every item including your assembly items. Just make sure to choose Autofill from Existing Inventory when creating your Sales Order.

You can read through these articles to learn more about advance inventory tracking:

• Use Serial or Lot Numbers
• Turn on Advanced Inventory

Let me know if you have other questions. I'm always here to help.