sql divide by zero error
Since your data types are already decimal types, perhaps you need to remove NULL values with a WHERE clause instead of coalescing them to 0, which would result in the "divide by zero" error.

Something like:

SELECT ((P.RealisedConsumption / (NULLIF((PO.ActualQty * P.QuantityPO), 0) 
    / NULLIF(10, 0))) - 1) * 100 AS FibreScrapFactor
FROM  &lt;...&gt;
WHERE PO.ActualQty IS NOT NULL
    AND P.QuantityPO IS NOT NULL