Fake discount detector: how to check if a deal is real, by hand or automatically

A fake discount detector compares the crossed-out price a retailer shows with the prices it actually charged before. To check a deal yourself, you need the product's price history: in France and across the EU, the reference price for a discount must be the lowest price the seller charged in the previous 30 days. If the "was" price is higher than what the product really cost, the discount is misleading.

What is a fake discount?

A fake discount is a price cut that looks better than it is. The most common forms:

• The inflated "was" price: the reference price was never charged, or only very briefly.
• The rise before the fall: the price goes up a few weeks before a big sales event, then "drops" back to its usual level.
• The discount off a list price: the percentage is based on a manufacturer's recommended price nobody actually pays.
• The permanent sale: the product is "on offer" almost all year at the same price.

Our guide to spotting a fake discount covers each case with its warning signs.

What does the 30-day rule say about "was" prices?

The EU Omnibus Directive introduced a rule on price reduction announcements. In France it has applied since 28 May 2022 under article L112-1-1 of the Consumer Code:

• any price reduction announcement must show the prior price charged by the seller;
• that prior price is the lowest price charged to all consumers in the 30 days before the reduction;
• for successive reductions over a set period, the prior price is the one before the first reduction;
• perishable goods likely to deteriorate quickly are exempt, and so are comparisons with other sellers' prices.

In other words, a "30% off" based on a price displayed for a single day two months ago doesn't meet the rule. Our article on the 30-day rule (Omnibus Directive) goes into the details. In France, you can report abuse to the DGCCRF, the consumer protection authority, through its public SignalConso platform.

How to check a discount by hand in 5 steps

1. Write down the "was" price and the sale price, with the date.
2. Find the product's price history at that retailer: your own notes, screenshots or a price history tool (for Amazon, see Amazon price history).
3. Look for the lowest price in the 30 days before the sale: that's the one that should be the reference.
4. Recalculate the real discount from that price, not from the crossed-out one.
5. Put the sale price in a longer context: is it close to the lowest price seen over several months, or just average?

Example: checking a deal against the price history

This is a purely illustrative example with hypothetical figures. A vacuum cleaner is shown at €299 instead of €449, "33% off". The history looks like this:

Period	Observed price (hypothetical)	What it shows
3 months ago	€339	The product's usual price
2 months ago	€329	Slight variation
3 weeks ago	€309	Lowest price in the last 30 days
Today	€299 (was €449)	The "was" price was never charged

Verdict: the legal reference price should be €309, not €449. The real drop is around 3%, not 33%. The price is still low, but it's not the exceptional deal advertised, so there's no reason to rush. Had this product been tracked in UniverTrack for three months, the €449 "was" price would be flagged as suspicious, because it's clearly above the highest price actually seen (€339).

Why checking by hand has limits

The method works, but it assumes you have data from before the sale. Yet you often discover a product on the very day it's "on sale". You'd need to have noted its price weeks earlier, do it again for every product and retailer, and redo the maths for each new offer. During Black Friday or the sales, when offers pile up, it quickly becomes unmanageable. That's exactly the job an automatic tool takes over.

How UniverTrack's fake discount detection works

Fake discount detection is included from the Smart plan upwards. Here's precisely what it does:

1. A real, dated price history

As soon as you track a product, UniverTrack checks its price automatically at regular intervals and dates every reading. During those checks, it also picks up the crossed-out price shown by the retailer, when there is one.

2. A comparison with the highest price actually seen

The crossed-out price is compared with the highest price observed over the last 90 days (or 365 days if needed). If it's clearly above that, beyond a small tolerance margin, the product page shows a warning: the displayed reference price looks inflated, it exceeds the highest price actually seen recently.

3. The "good time to buy" indicator alongside

On the same page, the indicator places the current price against the lowest, average and highest prices seen. It tells you whether the "sale" price is genuinely low or just average, and shows Not enough data while the history is too short.

What the detector doesn't do

• It gives no legal verdict: it flags a suspicious "was" price, it doesn't rule on compliance with the 30-day rule.
• It catches clearly inflated "was" prices. A crossed-out price below the highest price seen but above the 30-day low isn't flagged: the price history on the page then lets you check it yourself in seconds.
• It needs a price history and a visible crossed-out price on the retailer's page. Outside Amazon, history starts on the day you track, so add the products you want before big sales events.

Checking by hand or using a detector?

	By hand	With UniverTrack (Smart)
Price readings	You note them yourself, when you remember	Automatic, at regular intervals, dated
Suspicious "was" price	You spot it and do the maths	Warning shown on the product page
Is the sale price really low?	Manual comparison with your notes	Indicator against lowest, average and highest
Number of products	A handful at best	Up to 50 products on Smart
Price drops	You have to keep checking	Email alert at your target price

Put it into practice: stop paying for fake discounts

1. Paste the link of each product you plan to buy into UniverTrack, ideally several weeks before the sales or Black Friday.
2. Set a target price based on the history as it builds up.
3. Get the alert when the price hits it, check the warning and the indicator, then buy with confidence.

If catching fake discounts is what you're after, the Smart plan is the one: it adds inflated "was" price detection, up to 50 tracked products and the AI assistant. For a single purchase where the history alone is enough, Starter may do. Compare plans on the pricing page and start your 14-day free trial, with no commitment.