What does OOS-Inactive mean

Hi sales40,

Welcome to the UK Community for QuickBooks Online!

Sounds to me like you've came across one of your old VAT codes from your desktop product - pre-migrating to Online.

Any transactions in the current VAT quarter that have that code, are recommended to be updated to the correct codes which you can find information of here: https://quickbooks.intuit.com/community/VAT/Common-VAT-Codes/m-p/239529

If you have historical transactions with this on, don't worry too much - Load up your desktop and see your VAT Codes on there, to see what impact it will have had in your books.