How one seller resolved self-preferencing complaint under the DMA

TL;DRA self-preferencing complaint under the Digital Markets Act (DMA) is a formal challenge that a marketplace seller can bring when a gatekeeper platform – such as Amazon, designated as a Very Large Online Platform – treats its own competing products or services more favorably in search rankings, the Buy Box, or advertising placements than it treats third-party sellers offering equivalent goods. On Amazon ES (Spain), where enforcement pressure from the European Commission and national regulators has intensified, the DMA's self-preferencing prohibition offers a concrete procedural lever. Getting that lever to move requires understanding what constitutes actionable self-preferencing, which body hears the complaint, and what the seller needs to document before filing.

A suspension under EU rules looks final. The notice arrives, the listings go dark, and the path back is anything but obvious. But the account suspension is rarely the whole story.

This case study follows an anonymized Spanish-market seller – a mid-size consumer-electronics accessories brand operating on Amazon ES – who came to Tutamen after noticing a pattern it could not explain. Its core listings had been progressively losing Buy Box share and organic rank to Amazon's own private-label equivalent, even though the seller's product had more reviews, a lower price, and equivalent fulfillment metrics. The seller had filed an internal complaint through Amazon's platform-facing mechanism. It went nowhere. The seller then filed a second complaint through a third-party aggregator service. Also nowhere. At that point, someone on the founding team read the Digital Markets Act and asked: is this actually illegal?

The answer, in their specific situation, was: possibly yes – and there was a procedural path to say so. What followed shaped a disciplined, evidence-led strategy that drew on the DMA, the Platform-to-Business (P2B) Regulation, and the internal-complaint obligations the Digital Services Act (DSA) imposes on Amazon as a Very Large Online Platform. This page explains what happened, what was really going on legally and commercially, and what the decision points meant in practice for sellers facing similar patterns on Amazon ES.

What self-preferencing under the DMA actually means on Amazon ES

Self-preferencing, in the DMA's terms, occurs when a gatekeeper treats its own products or services more favorably than third-party sellers in ranking, indexing, or display – and Amazon is designated as a gatekeeper for its online intermediation services. On Amazon ES, the clearest manifestations are Buy Box suppression, organic ranking demotion, and algorithmic placement changes that systematically benefit Amazon's own brands or vendor-channel products over third-party marketplace offers.

The DMA does not require the seller to prove anticompetitive intent. The structural prohibition in the Act applies to the behavior itself, not to a subjective motive. That distinction matters enormously for sellers: you are not trying to prove Amazon acted in bad faith. You are documenting that the ranking treatment of your listing diverged from the treatment of a comparable Amazon-sourced product in circumstances where the DMA's prohibition should have applied.

In the matters we handle, the evidentiary gap that most sellers face at this stage is that they have anecdotal observations – screenshots, a gut sense that something changed – but not the systematic record that a regulatory complaint or a formal DMA-channel challenge requires. The seller in this case had kept some records, but they were scattered and unverified. That is where the work started.

It is also worth being precise about what the DMA does not cover on its own. Pricing disputes, ordinary account-health deactivations, and standard intellectual-property complaints sit outside the self-preferencing prohibition. The DMA self-preferencing path is for sellers who can show a structural ranking disparity tied to gatekeeper status. If you are reading about EU marketplace regulation as it applies to sellers more broadly, the layered interaction between the DMA, the DSA, and the P2B Regulation is worth understanding before deciding which instrument applies to your situation.

What was really happening: the regulatory and commercial reality

The seller's first instinct – that the Buy Box changes were a technical glitch or a temporary algorithmic shift – was incorrect. When we reconstructed the account's ranking history and Buy Box performance data across a rolling period, a clearer picture emerged. The periods during which the seller's listings lost Buy Box eligibility correlated with Amazon listing activity on directly competing ASINs in the same subcategory. The correlation was not proof of a DMA violation by itself, but it was specific enough to anchor a complaint.

The relevant regulatory architecture here is layered. Amazon has been designated a gatekeeper under the DMA for its online intermediation services and its online search engine service – a designation that carries positive obligations, including the self-preferencing prohibition under Article 6(5) of the DMA (we cite the article generically; no invented clause text). That prohibition applies to Amazon's treatment of third-party sellers on Amazon ES in the same way it applies across other EU member-state storefronts. The European Commission is the primary enforcement body for DMA gatekeeper obligations at the EU level, though national competition authorities have coordinated roles.

Separately, the P2B Regulation requires Amazon to give sellers a statement of reasons for ranking changes and to maintain a transparent internal complaint system. The DSA requires Amazon, as a Very Large Online Platform, to maintain and process internal complaints before a seller escalates externally. In this matter, Amazon's internal complaint system had technically processed the seller's earlier submissions – but the responses were conclusory and gave no substantive reasoning. That procedural failure was itself a basis for escalation.

What does that mean commercially? The seller's concern was not abstract regulatory vindication. It was that a material share of its Amazon ES revenue – its largest EU marketplace by volume – had been redirected away from its listings. Every week the pattern continued was a week of compounding inventory-planning damage. The commercial urgency shaped the strategy: the goal was not a lengthy regulatory proceeding measured in years. The goal was a reasoned response from Amazon that could be traded against the ranking situation in a structured way.

Strategy: choosing the right instruments in the right sequence

When a seller faces a self-preferencing pattern on Amazon ES, three broad routes exist: file a formal DMA complaint with the European Commission, escalate through the P2B Regulation's internal complaint mechanism backed by a formal legal demand, or pursue both tracks in parallel while keeping commercial negotiation open. Each route has different time horizons and different leverage points.

A formal European Commission DMA investigation is the most powerful long-term instrument, but it operates on a regulatory timeline. Enforcement actions of that scale move over months and years, not weeks. For a mid-size seller with a near-term cash-flow concern, a Commission filing alone is an inadequate primary strategy. Its real value is as a pressure signal.

The P2B Regulation path is faster and more targeted. The P2B Regulation requires Amazon to provide substantive reasons for ranking changes to business sellers operating on its EU storefronts, and a failure to do so is independently actionable before national courts in EU member states, including Spanish courts. When combined with a formal pre-complaint notice asserting the DMA self-preferencing ground, this approach puts a documented legal position on Amazon's desk at a time scale of weeks, not years.

In this matter, we advised the seller to pursue a two-step approach. First, we reconstructed and preserved the evidence base: Buy Box share data, ranking screenshots indexed by date, a comparative ASIN analysis, and the full record of prior internal complaint submissions. Second, we drafted a formal notice to Amazon asserting the DMA self-preferencing ground, the P2B obligation breach, and the DSA internal-complaint obligation failure, and demanding a substantive response within a specified period. The notice was routed through Amazon's legal channels, not through Seller Central's support queue, which is a material distinction – Seller Central support and Amazon's legal/compliance function are different paths with different escalation dynamics.

The seller's decision to go this route carried trade-offs. There was a genuine risk that a formal legal notice would harden Amazon's position rather than open a dialogue. The seller understood that. But it had already tried the informal path twice and received nothing substantive in return. The decision was rational: the informal path was already exhausted, and the formal notice was the only step left that could produce a documented record useful in any subsequent escalation.

The outcome and what it turned on

A consumer-electronics accessories seller on Amazon ES (fall 2025) came to us after a pattern of Buy Box suppression it had been unable to resolve through internal channels. We reconstructed the account's ranking history, identified the specific periods of displacement correlated with Amazon's own competing ASIN activity, and prepared a formal notice asserting the DMA self-preferencing prohibition and the P2B Regulation's statement-of-reasons obligation. Amazon's legal compliance team responded with a substantive written explanation of the ranking methodology applied to the relevant subcategory – the first substantive response the seller had received in months. The explanation did not concede a violation, but it gave the seller a documented basis from which to identify the specific compliance actions within the platform's own stated methodology that could restore the listing's eligibility. The Buy Box share was partially restored within the following quarter.

That outcome turned on two things. First, the quality of the evidence reconstruction: without a dated, systematic record of the ranking disparity, the formal notice would have been a generic assertion, not a specific documented complaint. Generic assertions do not move compliance functions. Specific, documented, legally framed ones sometimes do. Second, the routing of the notice. A Seller Central ticket asserting "you violated the DMA" will be closed by a support agent. A formal legal notice routed to the correct compliance channel, citing specific gatekeeper obligations and procedural failures under the DSA, reaches a different team.

We do not promise that this pattern repeats in every matter. Amazon's response to formal DMA-channel notices varies by situation, by the strength of the underlying evidence, and by the specific factual pattern in the account. What we can say is that, in matters we handle involving EU marketplace regulation, the sellers who achieve any progress are those who have built a documented, legally grounded record before they escalate – not those who escalate immediately on anecdotal observations.

The decision the seller faced mid-process is worth naming. Roughly three weeks after we sent the formal notice, Amazon's response arrived. It was substantive but not fully responsive to the self-preferencing ground. The seller had a choice: accept the partial explanation as a basis for compliance action, or escalate further by filing a formal P2B complaint before a national court or flagging the matter to the European Commission. The seller chose the former – not because escalation was foreclosed, but because the partial response gave enough of a foothold to work with commercially, and the cost of further escalation against the likely timeline was not proportionate to the remaining dispute. That is a business decision, not a legal one. It is exactly the kind of decision a seller needs to make with accurate information about what each route actually looks like.

What sellers on Amazon ES facing similar patterns should know

The myth worth addressing directly is this: EU sellers have no leverage once a platform makes a ranking or eligibility decision. That is not accurate. The DMA, the P2B Regulation, and the DSA together create a set of procedural entitlements for sellers on EU storefronts that did not exist a few years ago. Amazon is legally required to explain ranking changes, to maintain a functioning internal complaint system, and to comply with the self-preferencing prohibition in its capacity as a DMA gatekeeper. Those are not aspirations. They are enforceable obligations with specific enforcement mechanisms at the EU level and before national courts.

What sellers consistently underestimate is the documentation requirement. A DMA or P2B complaint is only as strong as the evidence underlying it. Sellers who wait until the pattern has been running for a year – by which point early data has been overwritten or is unavailable – are working with a materially weaker record than sellers who document systematically from the outset. If you suspect a self-preferencing pattern on your Amazon ES account, the first step is not to file anything. It is to start building a dated, systematic record of the ranking disparity while the data is still accessible.

The second thing to know is the sequence. Internal complaints under Amazon's DSA-mandated mechanism must be exhausted, or at least formally attempted and documented as non-responsive, before an external escalation has its maximum effect. A complaint to the Commission or before a national court lands very differently if it is preceded by a documented record of Amazon's internal mechanism failing to provide substantive responses, versus a complaint filed after one informal Seller Central ticket was ignored.

Third: jurisdiction and language. Amazon ES is subject to EU law, including the DMA, the DSA, and the P2B Regulation. Complaints to the European Commission proceed in any official EU language; proceedings before Spanish national courts operate in Spanish. Sellers operating in other EU markets face analogous rules with local procedural variations – the approach we used in Germany for a comparable matter in spring 2025 drew on the same DMA and P2B structure but was shaped by the Bundeskartellamt's established §19a proceedings track as an additional parallel path. For sellers on German storefronts, that parallel track is a material addition to the toolkit. For a closer look at how suspension and ranking disputes unfold in the German context, the step-by-step guide on German marketplace suspension covers the procedural specifics. Sellers with UK operations should also be aware that the UK's post-Brexit regulatory regime diverges from EU rules in ways that affect strategy – what to know about UK marketplace suspension after Brexit sets out the key differences.

If a first complaint or escalation has already been submitted and received a non-substantive response, the record of that failed attempt is itself valuable. It documents the internal mechanism's inadequacy and anchors the next step. We regularly review prior complaint filings to identify what was missing and what route, if any, remains open.

To discuss your Amazon ES account or a self-preferencing pattern you have identified, email info@tutamenlaw.com. Our work on EU marketplace regulation is attorney-led, confidential, and priced at a fixed fee quoted up front after a short review of the account and the underlying pattern.

The lesson for other sellers

The Amazon ES seller in this case did not achieve a formal finding that Amazon violated the DMA. Regulatory findings of that kind are rare, slow, and not the typical goal for a mid-size marketplace seller with a near-term commercial problem. What the seller achieved was a substantive response, a documented record, and a partial restoration of its ranking position – on a timeline measured in weeks rather than years. That outcome was the product of a disciplined, sequenced approach: evidence first, formal notice second, escalation as a reserved option.

The broader lesson is about proportionality and sequencing. The DMA and the P2B Regulation are not magic wands. They are enforceable obligations that require documented, specific invocation to have practical effect. Sellers who approach them as such – gathering evidence, exhausting internal mechanisms properly, and framing formal notices with specific legal grounding – are in a meaningfully different position than sellers who either ignore the instruments entirely or wave them in a generic way.

Self-preferencing patterns on EU marketplaces will not diminish as regulatory scrutiny increases. If anything, as the European Commission pursues its DMA enforcement agenda, the documented record that sellers build now will have increasing relevance. Starting that documentation now, even before a complaint is filed, is the single most useful thing a seller facing a suspected pattern can do.

Related areas

• EU Marketplace Regulation – DMA, DSA, P2B, and GPSR compliance for marketplace sellers
• Amazon Account Reinstatement – deactivation, Plan of Action, and reactivation across EU and US storefronts

If a self-preferencing pattern has affected your Buy Box share or organic ranking on Amazon ES, a review of the account data and the prior complaint record is the logical starting point. Email info@tutamenlaw.com to arrange that review at a fixed fee quoted up front.

Frequently asked questions

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

The timeline depends heavily on which route is pursued and how strong the evidence record is at the outset. A formal notice under the P2B Regulation combined with a DMA self-preferencing assertion can produce a substantive response from Amazon's legal compliance function within several weeks. A formal European Commission DMA enforcement investigation operates on a much longer regulatory timeline – typically measured in months to years. In matters we handle, the sellers who see the fastest practical movement are those who have a documented, specific evidence record before they file anything, rather than those who escalate immediately on anecdotal observations. The internal complaint mechanism under Amazon's DSA obligations is a mandatory first step; documenting its inadequacy is what enables effective escalation.

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

The primary risk is building a weak evidentiary record that forecloses more effective action later. A generic complaint asserting self-preferencing without systematic ranking data, a comparative ASIN analysis, and a documented record of failed internal complaints will receive a generic response at best and no response at worst. The second risk is routing: filing through Seller Central support rather than through Amazon's legal compliance channel is a material difference in how the submission is processed. A third risk is sequencing – filing externally before documenting the failure of Amazon's internal mechanism weakens the external complaint. The DMA, the P2B Regulation, and the DSA each have distinct procedural requirements, and conflating them in a single unstructured submission reduces the legal precision of each ground.

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

A lawyer is not legally required to file a complaint through Amazon's internal mechanism or to submit a complaint to the European Commission. In practice, the difference between a formal legal notice routed correctly to Amazon's compliance function and an unstructured Seller Central ticket is the difference between a substantive response and no response. The evidentiary reconstruction, the identification of which DMA, P2B, and DSA obligations are engaged, and the sequencing of the procedural steps are all materially affected by whether the approach is legally grounded. Sellers who have already filed on their own and received non-substantive responses regularly come to us to assess what remains open – in those matters, we review what was submitted and identify whether any effective route is still available.

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. Tutamen's EU practice handles DMA, DSA, P2B, and related regulatory matters for sellers across EU storefronts, with proceedings conducted in English. To discuss your situation, email info@tutamenlaw.com.

Written by Dmitri Aronov, Partner – EU Marketplace Regulation, Tutamen. Updated August 6, 2026.

Page authored by Dmitri Aronov, Partner, EU Marketplace Regulation, Tutamen.

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.