Sources, method, privacy and limits

How the checker reaches its results, where each rule comes from, and where it stops.

By Adam Hale · updated 2026-10-12

Method

1. Reading the files. Prices become whole cents (or the currency's minor unit), so comparisons are exact. Ambiguous prices such as 1,299 and ambiguous dates such as 05/06/2026 are refused rather than guessed. Rows that cannot be read are listed with their line numbers and skipped.
2. Building the price timeline per SKU, channel and currency. In change-log mode a price holds until the next row; in daily mode each row is one day and missing days are reported. Prices recorded at the same moment all count. Planned sale steps earlier in your sale file are added to the timeline, and, where an earlier step has an end date, the price is assumed to return to its pre-sale level afterwards.
3. The window runs from 30 local calendar days before the sale start to the start itself, in the sale country's time zone, unless a national option changes it (perishables, new products, progressive steps). The lowest price that applied at any moment in that window is the prior price (Article 6a).
4. Checks. The sale price must be below the prior price; a planned “was” price must not be above it (a lower one is allowed, guidance section 2.1); an advertised percentage must not exceed the reduction from the prior price (C-330/23).
5. Evidence. Results, settings, the rules applied and the SHA-256 of the input files are written to a hash chain and signed (see verify).

What the checker cannot know

• Whether your history is complete and true. It can only see the rows you give it.
• Whether a promotion counts as a price reduction announcement, a loyalty scheme, a personalised discount or a comparison with an RRP. It assumes every row in the sale file is an announced reduction of goods to consumers.
• Whether a perishable exemption's condition is met (for example, that the price is cut because the food is about to expire), or whether a product falls in a designated Dutch category.
• Below-cost sales in Italy and food-waste prices in Spain, which do not count towards the prior price there. Remove those rows first.
• Options of EU/EEA countries other than France, Germany, Austria, the Netherlands, Poland, Italy and Spain, Northern Ireland, and enforcement practice or court decisions after 2026-10-12.
• Rules for unit prices, which Article 6a also covers for goods sold in bulk. Check unit prices separately.

Privacy

The site is static files on Cloudflare Workers. Your CSV files are read with the browser's File API and processed by JavaScript on this page; they are never sent anywhere. The site sets no cookies, has no analytics and loads no third-party scripts, fonts or images; its Content Security Policy allows connections only to this site (to fetch the sample files). The signing key for evidence files is created in your browser and stored in its IndexedDB; a bulk licence key, if you enter one, is stored in its local storage. Cloudflare, as host, processes the usual request data (IP address, user agent) to serve the pages. Contact: adam.hale@atomicmail.ai.

All sources

The full list, with access dates and the exact quotations used, is in the list below. National texts were read in their original language; quotations on this site are translated by us. The French article was read from the Internet Archive's copy of the Légifrance page, because Légifrance blocks automated readers. France (DGCCRF guidance) · Germany · Austria · Netherlands (perishable categories) · Poland · Italy · Spain · UK DMCC Act s. 226 · CMA207 · CMA open letter · Price Marking (Amendment) Order 2024.

Disclaimer

This is a workflow aid, not legal advice. It does not certify that any price claim is lawful. The rules were read in the official texts on 2026-10-12 and may change. You remain responsible for your prices; for a specific case, ask a lawyer or your national consumer authority.