Maintenance of cost of sales not released. Check entry

What causes this issue?

You can only enter an amount for the <GL:cost_of_sales>cost of sales</>
if the <LS>COS freely def.</> indicator is set.
If that indicator is not set, the cost of sales is calculated
automatically using the following formula:
Cost of sales = actual costs - capitalized costs/work in process +
reserves for unrealized costs

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Check your entry.
To enter an amount for the cost of sales that differs from the above
formula, go into Customizing and set the <LS>COS freely def.</>
indicator in the expert mode of the valuation method.

Error message extract from SAP system. Copyright SAP SE.