Summary · 2 min read
The 30-day pricing rule requires retailers to base any advertised discount on the lowest price charged in the previous 30 days. Get it wrong and you risk fines from consumer authorities across the EU and the UK before your next Black Friday campaign.
- The reference price is the lowest price charged in 30 days
- EU sweeps found 30% of retailers non-compliant
- Automated price logging removes the guesswork and the risk
If you sell online anywhere in Europe, the 30-day pricing rule decides whether your Black Friday discount is a genuine offer or a fine waiting to happen.
A recent EU-wide sweep of 314 online traders found that 30% presented discounts incorrectly. For a retailer, that means reputational damage, legal costs and hours spent fixing prices under pressure right before a peak sales weekend.
What is the 30-day pricing rule and when does the clock start?
The 30-day pricing rule is the requirement that any advertised discount must be based on the lowest price a retailer charged in the 30 consecutive days immediately before the price cut, not an inflated “was” price invented for the sale.
Across the EU (including the Netherlands, Austria, Denmark and Finland) this comes from the Price Indications Directive as transposed under the Omnibus reforms. Portugal implemented the same standard through Decree-Law 109-G/2021, a useful illustration since onOrbit Marketing’s e-commerce team is based there and applies it daily for clients selling across borders.
The 30 days are counted from the day before the new reduced price takes effect, not from the start of your marketing campaign and not from the date a customer bought the item. The rule applies the same way to sales, promotions and clearance events, on any channel.
UK, EU and Portugal side by side
| Market | Legal basis | Reference price | Enforcement body |
|---|---|---|---|
| EU (NL, AT, DK, FI) | Price Indications Directive / Omnibus | Lowest price in 30 days | National consumer authority |
| United Kingdom | Digital Markets, Competition and Consumers Act 2024 | Set by CMA guidance and CAP Codes | CMA / ASA |
| Portugal (EU example) | Decree-Law 109-G/2021 | Lowest price in 30 days | ASAE |
The UK left the EU regime behind, but under the Digital Markets, Competition and Consumers Act 2024, GB retailers still face strict was/now pricing compliance obligations, policed by the CMA and the ASA.
Why merchants get the 30-day pricing rule wrong
Run this quick self-check before your next campaign:
- You are not sure which date to start counting 30 days from
- Your website, marketplace listing and physical store show different prices
- You change prices manually with no record kept of previous ones
- You treat brand-new products as if they already had price history
- You assume showing the discount percentage is optional
Any one of these, on its own, is enough to breach the 30-day pricing rule without any intention to mislead anyone.
How to calculate a legal discount under the 30-day pricing rule
To calculate a Black Friday discount correctly, you must use the lowest price applied during the 30 consecutive days preceding the price reduction, including any promotions offered during that period. You should not calculate the discount based on the original price unless it also qualifies as the legally applicable reference price.
The formula is: Discount (%) = [(Reference price − Promotional price) ÷ Reference price] × 100. Before launching your campaign, check each product’s price history and keep records that substantiate the reference price used.
Example: Calculating a Legal Discount
€89.90
€79.90
€69.90
Illustrative example. The reference price must correspond to the lowest price legally applicable during the relevant reference period. Always verify your price history before advertising a discount.
Alona Stepanova
CEO of onOrbit Marketing | Web Developer & Specialist in E-commerce Growth. Helps SMEs and online stores in Portugal and across Europe grow with web development, SEO, GEO and digital marketing.