A. Create a CSV File for the Item Record (CSV File may contain Item Name/Number, or Item Internal ID).
B. Perform the CSV Import Process.
1. Navigate to Setup > Import/Export > Import CSV Records.
2. Import Type - Items; Record Type - Inventory Items.
3. Upload the CSV File.
4. Click Next.
5. Set Data Handling as Update.
6. Click Next.
7. Map the CSV Fields with the NetSuite Fields:
Internal ID <=> Internal ID (or Item Name/Number - Item Name/Number)
(Choose Default value = Parent Subsidiary) <=> Subsidiary
(Choose Default value set to Yes) <=> Include Children
8. Click Next.
9. Assign an Import Map Name.
10. Click Save and Run.
Note: Item records are now associated to all the Subsidiaries and can now be used in transactions regardless of Subsidiary.