Four displayed values describe one transaction
In percentage mode, original price, percent off, sale price, and savings are linked by one relationship. Entering any valid independent pair can identify the remaining two: original plus rate works forward, original plus sale price reveals savings and effective rate, while sale price plus savings reconstructs the original. The ability to solve backward is useful when a receipt shows dollars but an advertisement emphasizes a percentage.
Independence matters. Fixed amount off and savings name the same quantity, so those two numbers alone cannot identify a starting or ending price. Similarly, a zero saved amount and a zero rate do not reveal the price of the item. The calculator should reject an underdetermined pair rather than manufacture a plausible original price.
Keep unrounded values until the final display. On a $59.99 item, a percentage can create fractions of a cent; a merchant may publish or settle according to a specific currency rounding policy. The audit should reproduce that policy explicitly when a one-cent discrepancy matters.
Choose fixed dollars or a percentage for the promotion actually offered
Percentage reduction
The dollar savings scale with the reference price. A twenty-percent offer saves more dollars on a higher-priced item, and it can be reversed when the sale price and rate uniquely determine the original. Use this mode only for one percentage stage.
Fixed-dollar reduction
The advertised amount is subtracted directly. Its effective percentage depends on the original price, so '$20 off' can be a modest reduction for one basket and a large reduction for another. Minimum-spend rules and category exclusions remain outside the arithmetic unless separately checked.
Sequential percentage campaign
When a checkout applies a second percentage to an already reduced price, use the Percent Off Calculator to preserve both stages. Adding the printed percentages directly usually overstates the combined saving.
Interrogate the advertised reference price
Correct arithmetic does not prove that a former, regular, comparable, or list price is an honest comparison.
- Record the exact product, size, quantity, condition, seller, channel, and date attached to both the reference and sale prices.
- Distinguish the seller's own former price from a manufacturer's suggested price, a competitor price, or a future price; the labels do not mean the same thing.
- Check whether membership, subscription, payment method, coupon code, minimum basket, or limited inventory changes who can obtain the displayed reduction.
- Treat strikethrough formatting and a mathematically correct percentage as claims that still require truthful substantiation under applicable advertising rules.
Trace the promotion from list price to settled proceeds
- Establish the cost-based list price separately
If the seller is designing rather than auditing the offer, first use the Markup Calculator to build a proposed selling price from a documented unit-cost basis. Do not present a price created moments ago solely to support a dramatic markdown as an established former price.
- Apply exactly one promotion rule
Choose the fixed or percentage mode that matches the offer, enter two independent values, and verify that savings plus sale price returns to the same original. Preserve coupon caps, thresholds, and item exclusions as separate conditions.
- Test the remaining gross margin
Send the actual checkout revenue and consistent direct cost to the Margin Calculator. The promotion's effective discount is not a profitability result, and a high sales volume does not rescue an offer that loses money on every incremental unit without another documented benefit.
- Reconcile the payment settlement
When a processor fee is deducted after checkout, model the declared fee separately with the payment fee calculator. This prevents a seller from calling the processor deduction part of the customer discount or counting the same reduction twice.
Keep checkout additions outside the markdown equation
The discount relationship ordinarily describes merchandise price before separately imposed tax, shipping, service fees, tips, financing charges, rebates, or post-purchase rewards. An offer may state otherwise, but the calculation must follow the written terms instead of guessing which additions receive the reduction.
For consumer verification, save the advertisement, item page, cart, coupon terms, and final receipt. For merchant review, retain the approved campaign rule, price history, eligible SKU list, settlement report, and margin analysis. Together those records answer both questions: was the arithmetic right, and was the price comparison represented truthfully?