Define the result being compared
Turnover, volume and the result after costs answer different questions. More units sold do not establish profitability if the commercial terms became substantially more expensive.
Define the calculation scope beforehand: products, customers, period and included costs. This prevents the meaning of the comparison changing after the campaign.
Bring the agreed costs together
Beyond an invoice discount, free goods, later bonuses and other agreed expenditure may matter. Apply product costs and commercial costs consistently, checking that the same item is not counted twice.
If some settlements remain unknown, show that limitation. An initial assessment is different from a calculation after the costs are complete.
Separate the result from the campaign's impact
Sales may also change because of seasonality, availability or an unusually large customer order. A previous period provides context without proving that the promotion caused the entire difference.
This information is especially useful to finance teams assessing commercial spending. Trade Marketing connects turnover, terms and their costs. It provides a more consistent basis for another campaign decision than sales growth alone.