A price reduction is the gap between a product's compare-at price and what it actually sold for: a markdown made by changing the price rather than by issuing a code. It never appears as a discount line in most reports, which is why price erosion is the quietest way a catalogue loses margin.
Two stores can run identical promotions and report completely different discount figures. One lowers the price and shows a compare-at price beside it; the other issues a code at checkout. The second appears in every discount report, and the first appears in none of them unless a statement measures it deliberately.
That is why a P&L worth reading has a separate line for it. Measured against the ticket value of what was ordered, price reductions show how much of the catalogue is habitually selling below its own list price, which is a different management question from how generous the codes are.
One safeguard matters in the data: when a compare-at price sits below the selling price, the reduction is treated as zero rather than as a negative. Bad catalogue data can otherwise inflate revenue, and a statement should never be improvable by a mistake in a product record.
