What is the nature of Offset, inventory write off and cost variance account in cost accounting

Summary:

We have recently gone live. As part of the cutover, there was a blackout period, due to which users are posting backdated transactions for WIP, Inventory and Sales Dispatches.

Due to this, we have observed system asking for offset account for WIP material issue and Inter Org shipments.

Due to a WIP product return, system triggered WIP Product Cost Adjustment, which requires Cost variance and inventory write off accounts.

Customer is using perpetual average. I want to understand what should be the nature of these accounts. How to handle these in GL and trial balance. Are these account of expense nature or asset ?