The Co-product indicator is not set on the BOM item under which the by-product is entered; instead, a negative quantity is entered.
Check Point 1-Check if By product is indicated as relevant to costing?
the total costs for the process are reduced by the amount of the costs of the by-product.
there are two ways to calculate
A price from the material master is used. The cost of goods manufactured for the by-products are arrived at by multiplying the output quantity by the price, and they appear in the itemization of the cost estimate with a negative value.
The by-product can be manufactured using an alternative production structure, and there is already a corresponding cost estimate for the by-product. In this case, this cost component split of the by-product is subtracted, cost component by cost component. The cost of goods manufactured for the by-products is arrived at by multiplying the output quantity by the costing results of the by-product from the alternative cost estimate.
I hope it helps
Best regards
Hrushikesh