This can be accomplished through CSVImport.
First part is to create a saved search.
Note: Enable Show Internal IDs in Home > Set Preferences> General tab > Defaults section.
1. Navigate to Lists > Search > SavedSearches > New.
2. Select Transaction.
3. In the Criteria tab> Standard subtab, set the following:
* Type is Sales Order
* Shipping Line is false
* Tax Line is false
* Main Line is false
* Add other required fields
4. In the Results tab> Columns subtab, click Remove All.
5. Add thefollowing fields:
* Line ID
6. Click Preview.
7. Click Export- CSV.
8. Savethe CSV file.
Second part is to update the CSV file.
1. Openthe CSV file.
2. Set afilter to remove all lines with no Item.
3. Change thevalue of the column Closed from No to Yes.
4. Savethe CSV file.
Third part is to reimport the CSV fileto update the records in NetSuite.
1. Navigate to Setup > Import/Export > ImportCSV Records.
2. Select Transactions inthe Import Type field.
3. Select SalesOrder in the Record Type field.
4. Click Select.
5. Locate theCSV file, then click Open.
6. Click Next.
7. Select Update for DataHandling.
* Under Advanced Options, make sure that the Custom Form being used has the "Closed" column exposed under the Screen Fields tab>Columns subtab of the said Custom Form.
8. Click Next.
9. In the FieldMapping section, set the following:
10. Click Next.
11. Provide an Import Map Name.
12. Click Save & Run.
Note: Enhancement 62556 has been filed for the ability to performtransactional mass update to close sales orders in bulk.