Self-preferencing complaint under the DMA: what to do, step by step

A seller on Amazon ES notices that Amazon's own private-label product consistently appears above their listing – even when the third-party product has stronger reviews, a lower price, and faster delivery. The sales drop. The Buy Box moves. The lost opportunity is real and ongoing, not hypothetical. For sellers in this position, the Digital Markets Act (DMA) now provides a concrete legal path that did not exist a few years ago.

TL;DRA self-preferencing complaint under the DMA is a formal challenge to a gatekeeper platform's practice of ranking or displaying its own products, services, or data more favorably than those of third-party sellers. On Amazon ES, this means invoking Article 6(5) of the DMA, which prohibits Amazon – as a designated gatekeeper – from using non-public seller data to favor its own competing offers, and from giving its own listings a systematic ranking advantage. The realistic procedural paths run through the European Commission, Spain's competition authority (CNMC), and Amazon's own internal complaint channel, each with different timelines and leverage points.

This guide walks through each step in sequence: what the complaint actually covers, how to build the record, which authority to approach first, and the three decision points where sellers most often lose momentum or make a mistake they cannot reverse.

What does self-preferencing mean under the DMA, and who does it cover?

Self-preferencing under the DMA means that a gatekeeper treats its own products, services, or data more favorably in ranking, display, or access conditions than equivalent third-party offerings – and it is prohibited, not merely suspect. Amazon was formally designated a gatekeeper under the DMA, meaning the prohibition applies directly to its operations across the EU, including Amazon ES. The DMA is not a general fairness principle: it contains specific, enforceable obligations with the European Commission as the primary enforcer and national competition authorities as co-enforcers.

For a seller on Amazon ES, the relevant conduct can take several forms. Amazon may rank its own Amazon Basics products above third-party equivalents in organic search results. It may give its private-label products preferential placement in "sponsored" positions funded, in effect, by the sellers whose money flows into Amazon's advertising business. It may use aggregated third-party seller data – sales velocity, return rates, customer search behavior – to inform its own product decisions, in ways that the platform denies to individual sellers. Each of these can form the factual basis of a complaint.

The P2B Regulation (Regulation (EU) 2019/1150) adds a parallel layer. It requires Amazon to give sellers written reasons for ranking decisions and to publish the main parameters governing ranking. A discrepancy between those published parameters and what sellers actually observe in practice – Amazon's own products ranking well despite weaker seller metrics – is itself useful evidence in a DMA complaint.

In matters we handle on Amazon ES, we regularly see sellers who have gathered anecdotal evidence of ranking suppression but have not connected it to the DMA's specific prohibitions. The gap between "Amazon seems to favor its own products" and "here is a documented, repeatable pattern that meets the Article 6(5) standard" is the most important gap to close before filing anything.

Step 1 – Build the evidentiary record before you file anything

The quality of your evidence determines whether the complaint moves forward or is closed without investigation, so building the record is not preparation – it is the first substantive step. Start by documenting the specific ranking pattern: screenshot the search result page on Amazon ES for your primary keywords, showing the position of your listing and Amazon's competing listing, with timestamps. Do this consistently over a period of weeks. One data point is noise; a pattern over time is evidence.

Alongside the screenshots, pull your Seller Central performance data for the same period. Note your conversion rate, star rating, number of reviews, pricing relative to Amazon's competing product, and Prime eligibility status. If your product outperforms Amazon's on every metric a reasonable buyer would weigh and still ranks below it consistently, that disparity is the core of your case.

Next, check the ranking parameters Amazon publishes under its P2B obligations. Amazon is required to disclose the main parameters determining ranking and the relative importance of those parameters. If those published parameters do not explain why Amazon's product ranks above yours given your comparative metrics, document that gap. Inconsistency between stated policy and observed outcome is probative.

A note on timing: evidence gathered before a filing carries more weight than evidence gathered after the other side knows a complaint is coming. In our practice, sellers who start documenting only after the complaint is filed often find their record thin at the critical early stage when the reviewing authority is deciding whether to open a formal investigation.

Also preserve any communications with Amazon that touch on ranking policy, account health, or advertising requirements. If Amazon has told you that spending more on Sponsored Products will improve your visibility, document it. The DMA draws a line between legitimate commercial features and using market power to coerce advertising spend in exchange for fair ranking.

Step 2 – Engage Amazon's internal complaint mechanism first

Amazon is required under the DMA to operate an internal complaint-handling system for business users, and under the P2B Regulation that obligation predates the DMA. For a seller on Amazon ES, this means there is a formal channel – separate from Seller Central's standard support tickets – through which a DMA-based concern can be raised. Using it is not optional if you want to preserve the full procedural record for later escalation.

The internal complaint must be specific. Submit it in writing and state clearly: the conduct you believe violates Article 6(5) of the DMA; the documented evidence you rely on (attach the screenshots and the performance comparison); the outcome you are requesting (typically a transparent explanation of the ranking parameters applied to your listings, and a correction of the differential treatment). Keep a copy of the submission with the date and time stamp.

Amazon is required to handle this complaint within a reasonable time and to give you a reasoned response. "Reasonable time" under the P2B Regulation and the DMA's implementing practice is typically measured in weeks, not months, though the DMA does not set a hard calendar deadline for internal responses. If the response is substantive and corrects the conduct, the matter may resolve here. More commonly, the response is formal and general – it does not engage with the specific pattern you documented.

That response, however inadequate, is itself part of the record. It shows you engaged the platform's mechanism in good faith and that the mechanism did not resolve the issue. This is a prerequisite for the next step with the European Commission or the CNMC, and it demonstrates the reasonableness of your position. Do not skip this step to save time.

Step 3 – Escalate to the European Commission or the CNMC

After exhausting the internal mechanism, the two main external paths are a complaint to the European Commission's DMA enforcement unit and a referral to Spain's Comisión Nacional de los Mercados y la Competencia (CNMC). Understanding what each path does and does not offer is the critical decision point in the whole process.

The European Commission is the primary enforcer of the DMA against gatekeepers. It has the power to open a formal non-compliance investigation, impose interim measures, and ultimately fine Amazon at a scale that only a public authority can reach. However, the Commission does not adjudicate individual seller disputes. It investigates systemic conduct across the platform. Your complaint contributes to a Commission investigation; it does not produce a ruling in your favor on its own. The Commission may or may not open an investigation based on your submission, and even if it does, the timeline of a formal Commission proceeding is long – typically running across several years.

The CNMC operates under the DMA's decentralized enforcement model. National competition authorities in the EU may assist the Commission in DMA enforcement matters, and the CNMC has its own competition law toolkit – including authority under Spanish competition law and its obligations under the European Competition Network – that may be faster to activate for Spain-specific patterns. A parallel filing with the CNMC can provide additional pressure on Amazon at the national level and a separate procedural track.

In matters we handle involving Amazon ES, the most productive approach is usually to file a well-evidenced complaint with the Commission and inform the CNMC simultaneously, keeping the two submissions consistent and cross-referenced. The combination creates regulatory visibility at two levels and signals that the seller is a serious complainant, not a one-time filer who will disappear if ignored.

One point sellers regularly misunderstand: a DMA complaint to a public authority is not the same as a claim for damages in court. If you want monetary compensation for the harm the self-preferencing caused, a separate civil claim – in Spain or another competent EU member state – is the route. A successful Commission finding of non-compliance can support that civil claim, but it does not automatically award you anything. These are parallel tracks, and the decision about whether to pursue both simultaneously turns on your specific situation, your evidentiary record, and the scale of the commercial harm.

Step 4 – Prepare the formal complaint document

The Commission and the CNMC both expect a structured submission. A well-prepared complaint is shorter and more powerful than a long one – and a long, unfocused complaint is one of the most common ways sellers lose credibility at the intake stage. Each complaint should contain: a description of the seller's business and the affected listing category on Amazon ES; the specific DMA provision alleged to be violated (Article 6(5) is the primary provision for self-preferencing); a factual narrative tied to dates and documented evidence; a statement of what the seller tried through the internal mechanism and what the outcome was; and a clear articulation of the requested action.

Attach the evidential record you built in Step 1. Present it as a structured exhibit, not a raw screenshot dump. A comparison table showing your product's metrics against Amazon's competing product – using only data you can source directly from Seller Central and Amazon's public listings – is far more useful to an investigator than dozens of uncontextualized images.

If you are pursuing the CNMC path, Spanish procedural requirements may require the submission to be made in Spanish. Ensure the translation is accurate at the level of legal and commercial precision; a machine translation of a complaint about algorithmic ranking is likely to introduce ambiguities that an authority will note as a credibility concern.

Our practice builds these submissions from the structured evidence record outward, starting with the DMA-specific prohibition and building the factual case to fit the legal standard the enforcement authority will apply. That sequence – law first, then facts mapped to it – is different from the way sellers naturally want to tell the story ("here is what Amazon did to me"), and the difference matters to how an authority reads the complaint on first review.

Step 5 – Manage the process and your options while it runs

A DMA complaint to the European Commission is not a short process. Formal investigations, if opened, play out over a timeline that is measured in months to years. Sellers who file a complaint and then do nothing else while waiting are in a commercially exposed position: the ranking suppression continues, the lost opportunity accumulates, and the procedural clock moves slowly.

There are things you can do in parallel. First, Amazon's internal complaint mechanism is not a one-time channel. If the underlying conduct changes, escalates, or takes a new form, you can file an updated internal complaint reflecting the new conduct. Each new submission refreshes the record and creates a new obligation on Amazon to respond. Second, if the commercial harm is sufficiently documented, a civil damages claim in Spain – separate from the regulatory complaint – can run in parallel and may resolve faster than a Commission investigation. Third, the DSA's statement-of-reasons mechanism provides an additional lever: if Amazon makes a visibility or ranking decision that affects your account, you are entitled to a reason, and that reason can be compared against the DMA-based evidence of differential treatment.

What sellers cannot afford to do is let the procedural record go stale. An authority reviewing a complaint filed many months ago will look for evidence that the conduct is ongoing. Keep documenting. Keep screenshots dated. Keep the Seller Central performance data current. A complaint with live, recent evidence is a different matter from one resting on a six-month-old screenshot file.

An electronics accessories seller on Amazon ES (fall 2026) came to us with a well-articulated complaint that had been filed with Amazon's internal mechanism and received only a generic response. We reconstructed the evidentiary record from Seller Central data and P2B-mandated ranking disclosures, filed a structured complaint with the CNMC alongside a Commission submission, and opened a parallel line of correspondence with Amazon's legal team. The internal mechanism re-engaged at a different level within weeks, and the ranking pattern for the seller's primary category improved materially during the Commission's preliminary review period.

Where this goes wrong: the three most common failure points

Filing too early – before the evidentiary record is complete – is the single most common mistake. An authority that sees a complaint with thin, inconsistent documentation is unlikely to open a formal investigation, and a rejection at intake is harder to reverse than it looks. It is almost always better to spend two to four additional weeks completing the record than to file immediately after the first incident.

The second failure point is treating the internal complaint mechanism as a formality to be rushed. Sellers who file a generic internal complaint, receive a generic response, and immediately escalate externally are foregoing leverage. A specific, well-argued internal complaint can sometimes produce a direct correction without any external filing, and even when it does not, the specificity of that internal submission shapes how the authority reads the subsequent external complaint.

The third failure point is conflating the regulatory complaint with a damages claim. Many sellers file a DMA complaint expecting to receive compensation for lost sales. That is not what a Commission or CNMC investigation produces. If you want monetary relief, you need a civil claim. That claim can be supported by a regulatory finding, but it requires a separate legal strategy. Sellers who do not understand this distinction often feel that the regulatory process "failed" them when it was, in fact, doing exactly what it is designed to do.

There is also a persistent myth worth addressing directly: that EU sellers have no real leverage once a platform like Amazon has made a decision. That was more nearly true before the DMA and the P2B Regulation created enforceable obligations on gatekeepers. It is not accurate now. The DMA imposes specific, legally binding duties – including the obligation to justify ranking decisions and to handle complaints through a formal mechanism. Those duties are not decorative. They create procedural footholds that a well-prepared seller can use. The key is understanding which foothold applies to your specific situation and in what sequence to use it.

For a broader grounding in how EU marketplace rules apply to sellers across the region, our complete guide to EU marketplace regulation for sellers covers the full regulatory picture from the DMA to the DSA to the P2B Regulation. For sellers whose issues span Germany and Spain simultaneously, our guide to German marketplace suspensions addresses the specific procedural context there, including the Bundeskartellamt's parallel track. Sellers managing UK operations alongside EU ones will find that the post-Brexit picture differs meaningfully, as set out in our step-by-step guide to UK marketplace suspension after Brexit.

If a first internal complaint or initial filing has already come back with a generic or dismissive response, a second read of the documentation can identify the specific gap between what you submitted and what the authority or Amazon's compliance team needed to see. That gap is usually fixable.

To discuss your situation on Amazon ES, email info@tutamenlaw.com.

Related areas

• EU Marketplace Regulation – DMA, DSA, P2B, and gatekeeper obligations for sellers
• Account Reinstatement – restoring suspended Amazon and marketplace accounts

Frequently asked questions

How long does resolving self-preferencing complaint under the DMA usually take on Amazon ES?

Resolution timelines vary significantly depending on the path taken. Amazon's internal mechanism is typically measured in weeks for a first response, though the quality of that response varies widely. A CNMC referral may produce engagement within a few months. A formal European Commission investigation, if opened, runs on a timeline measured in months to years. Sellers should plan for the regulatory path to be long and maintain the commercial record throughout. Civil claims, if pursued in parallel, operate on Spanish civil procedure timelines and may resolve independently of the regulatory track.

What are the main risks if I handle self-preferencing complaint under the DMA alone?

The main risks are evidentiary, procedural, and strategic. Evidentiary: sellers often gather screenshots without connecting them to the specific DMA standard an authority applies, making the complaint easy to dismiss at intake. Procedural: the internal complaint mechanism, Commission filing, and CNMC referral each have specific form and content expectations; a poorly structured submission can be closed without substantive review. Strategic: conflating the regulatory complaint with a damages claim leads sellers to expect compensation that the regulatory process does not produce, and they may forgo the civil claim that could actually deliver it.

Do I need a lawyer for self-preferencing complaint under the DMA?

There is no formal legal requirement to be represented by a lawyer to file a DMA complaint with the European Commission or the CNMC. However, the practical answer for most sellers is that the quality of legal representation materially affects both the intake decision and the trajectory of the process. Building an evidentiary record that maps cleanly to Article 6(5)'s standard, navigating both the Commission and CNMC tracks simultaneously, and managing the parallel civil option all require legal judgment that goes beyond form-filling. DSA seller rights, the dma gatekeeper framework, and P2B Regulation procedural requirements interact in ways that are not intuitive without specialist knowledge of EU marketplace regulation.

About Tutamen

Tutamen is an independent law firm for online marketplace sellers. We represent Amazon, Walmart, Etsy and eBay sellers in account deactivations, frozen-funds recovery, intellectual-property disputes, arbitration and Notices of Dispute, and US federal Schedule A defense, plus EU marketplace regulation. Our work is attorney-led and confidential, with fees quoted up front. We act for founders, brand owners and in-house teams who need a specialist for a marketplace dispute. Our EU marketplace practice covers the full range of DMA, DSA, and P2B matters, with work conducted in English and Russian on request. To discuss your situation, email info@tutamenlaw.com.

Disclaimer: This article is general information, not legal advice, and does not create an attorney-client relationship. Marketplace policies and the law change, and every account and case is different. For advice on your situation, contact Tutamen at info@tutamenlaw.com.