Overhead and settlement in WIP

Hello,

We have a material and COGM for that is: 2000 and COGS is 2400. But we are updating the COGM only to Material master as standard price.

When we run the WIP and Settlement system is showing 400 as difference and it is going to Price Difference.

To avoid what we have to do.

1) Shall we need to maintain overheads in OKTZ as a inventory?

Thanks

Sateesh