Can't create Additional Cost in Stock Entry

Hi Everyone!

I’m quite confused. Our Labor Cost for our manufacturing process is outsourced. We buy the raw materials and our labor is done by a third-party contractor. Our practice is to pay the contractor in advance before the production.

So initially, we create invoice for the advance payment and recorded as follows:

Prepayments to contractors – Debit
Accounts Payable/Cash – Credit

However, when we do the stock entry at the end of the month, to record the portion of the expired prepayments as part of the additional cost, i can’t add entry anymore.

We have to reflect the portion of the Labor Cost on the project as well. The entry must reflect be:

Work-In-Progress - Debit
Prepayments to Contractor – Credit

I tried to do JE instead of including it as part of the Additional Cost in the Stock Entry. But I also can’t add.

How can I reflect the Labor Cost as part of the consumed cost of the Work-In-Progress Inventory?