Responding to self-preferencing complaint under the DMA the right way

TL;DRA self-preferencing complaint under the Digital Markets Act (DMA) is a formal challenge to a gatekeeper platform's practice of ranking or displaying its own products and services more favorably than those of third-party sellers. On Amazon ES, this can surface as a listing demotion, a Buy Box exclusion, or a visibility reduction that disadvantages independent sellers relative to Amazon's own retail arm. The DMA gives EU sellers concrete procedural rights they can use – but only if the complaint is filed in the right place, at the right level, and in the right sequence.

When an Amazon ES seller notices that a competing ASIN sold directly by Amazon's retail operation consistently captures the Buy Box or occupies top search placement despite comparable pricing, delivery performance, and seller metrics, the instinct is to treat it as an algorithm problem. It is not only that. It is a potential DMA violation – and the distinction changes the entire response strategy. As EU marketplace rules have moved from soft guidance to enforceable obligations with real enforcement teeth, sellers who understand the procedural path have options that most assume do not exist.

This guide sets out the exact step sequence for handling a self-preferencing complaint under the DMA on Amazon ES, the decision points where the matter branches, and the places where sellers acting alone most often lose ground they cannot recover.

What is a self-preferencing complaint under the DMA on Amazon ES?

Self-preferencing under the DMA is the practice by which a designated gatekeeper gives preferential treatment to its own services over those of competing business users operating on the same platform. Amazon is designated as a gatekeeper under the DMA, which means its obligations apply across the EU – including on Amazon ES. The specific prohibition on self-preferencing means that Amazon must not rank its own retail offers more favorably than comparable third-party offers using criteria that are not equally available and applied to all sellers.

In practice, on Amazon ES, self-preferencing can appear in several forms. The most commercially damaging is Buy Box suppression: a third-party seller matches or undercuts Amazon's own price, meets Amazon's fulfillment standards, and still does not win the Buy Box at a rate proportional to their offer quality. A second form is search-ranking demotion, where sponsored or organic placement for third-party ASINs is systematically lower than placement for Amazon-owned or Amazon-sold versions of the same or similar products. A third form, less visible but equally significant, is differential access to data – Amazon using aggregated seller data to position its own private-label products.

A self-preferencing complaint is different from a standard Amazon account appeal. It is not filed in Seller Central. It is not a Plan of Action. It operates through a separate procedural architecture built by the DMA and, below it, by the Platform-to-Business (P2B) Regulation and the Digital Services Act (DSA). Understanding which instrument covers which aspect of the complaint is the first decision a seller must make correctly – because filing in the wrong channel wastes time and, in some cases, waives procedural options.

A DMA complaint targets the gatekeeper's structural behavior. A P2B complaint targets contractual terms and ranking transparency. A DSA statement of reasons challenge targets a specific content or listing removal. On Amazon ES, a seller dealing with apparent self-preferencing will typically engage all three layers, but they do so in a specific sequence and with different objectives at each stage. For a broader view of how these instruments fit together, see our complete guide to EU marketplace regulation for sellers.

Step 1: Document the commercial harm before you file anything

The foundation of any DMA complaint is evidence, and evidence gathering must happen before any formal step – because the European Commission and national competent authorities expect a complaint to arrive with substantiation, not a general allegation. A seller who files a bare assertion that Amazon is self-preferencing will be asked for specifics. If those specifics are not ready, the complaint stalls.

What substantiation looks like in practice is a structured dataset. For Buy Box complaints, that means a time-series of Buy Box win rates for the seller's ASINs compared against price, delivery performance, and condition data for the competing Amazon retail offer. The data needs to span a period long enough to rule out promotional or seasonal anomalies – typically several weeks of consistent patterns. Screenshots alone are not sufficient. Exported reports from Seller Central's Business Reports section, timestamped and tied to specific ASINs, carry more weight.

For search-ranking complaints, the documentation should show sponsored and organic placement comparisons for the same or equivalent search terms, across multiple sessions and multiple dates. Amazon's ranking parameters are not publicly disclosed, so the evidence cannot directly prove the algorithm's logic – but it can demonstrate a pattern that is statistically inconsistent with the seller's offer quality and metrics.

The P2B Regulation's ranking transparency obligations are directly relevant here. Amazon ES is required to disclose the main parameters determining ranking and their relative importance. If the disclosed parameters do not account for the pattern the seller observes, that gap is itself part of the complaint. In matters we handle, the gap between Amazon's disclosed ranking methodology and observed outcomes is often the sharpest part of the argument.

Two practical points. First, preserve data before filing anything – once a formal complaint is lodged, Amazon may become aware of the specific account under scrutiny. Second, note every date on which the pattern was observed and any correspondence with Amazon that acknowledged or failed to explain the discrepancy. Unanswered seller inquiries about ranking methodology are useful exhibits.

Step 2: Use Amazon's internal complaint-handling system as a required first move

The DMA requires gatekeepers to establish an internal complaint-handling system for business users. Amazon's obligation to provide this mechanism is not optional – it is a DMA compliance requirement. Filing through that system is not merely a box to tick. It is a mandatory procedural step that creates a record, starts a clock, and sets up the escalation path.

A complaint filed through Amazon's internal system should be specific and formal in tone. It should identify the DMA obligation at issue – the prohibition on self-preferencing and the ranking transparency obligation under P2B – name the ASINs and time periods affected, set out the commercial harm in concrete terms, and request a reasoned response within the time period the DMA requires. Generic seller support tickets do not satisfy this requirement. The complaint needs to be lodged in a way that is clearly framed as a DMA/P2B complaint, not a standard seller dispute.

What sellers regularly get wrong at this step is the framing. A complaint that reads as "please fix my Buy Box" will be routed to seller support and answered with a templated non-response. A complaint that references the DMA self-preferencing prohibition, identifies the specific ranking conduct, and requests a statement of reasons under the DSA's internal complaint mechanism is a different document – and it is treated differently. In our practice, the quality of this first filing determines how much leverage the seller has in every subsequent step.

Amazon is required to respond, and to do so in a timely and non-discriminatory way. If the response is substantively inadequate – if it denies the issue without engaging the evidence, or provides a ranking explanation that does not account for the documented pattern – that inadequate response becomes Exhibit A in the next stage. Keep it. The timeline of requests and responses matters as much as the content of either.

Step 3: Escalate to the relevant national competent authority or the European Commission

If Amazon's internal complaint-handling process produces no adequate resolution, the DMA provides for escalation to the competent enforcement authority. The European Commission holds primary jurisdiction over gatekeeper obligations under the DMA. National competent authorities in EU member states can receive complaints and refer them, and in some matters can take independent action under national competition law running in parallel.

For an Amazon ES seller, the relevant national authority is Spain's Comisión Nacional de los Mercados y la Competencia (CNMC). The CNMC has powers under Spanish competition law that can run alongside, or in some circumstances supplement, DMA enforcement. The relationship between Commission-level DMA enforcement and national-level competition proceedings is still being worked out in practice – which means the sequencing of where a formal complaint lands first can affect the overall timeline and the remedies available.

A Commission complaint is a formal document. It requires identification of the complainant, the gatekeeper, the specific obligation alleged to be violated, the evidence, and the requested remedy. The Commission has discretion over which complaints it investigates as formal proceedings, and it prioritizes based on the systematic nature of the alleged violation and the availability of evidence. A single seller's complaint is less likely to trigger a standalone formal proceeding than a coordinated submission from multiple sellers documenting the same pattern. This is one reason why the evidence-gathering stage matters so much – a well-documented complaint from one seller can prompt the Commission to widen its inquiry and reference findings from existing open proceedings.

In parallel, sellers should consider whether the conduct also supports a P2B complaint regarding the adequacy of ranking transparency disclosure. The P2B enforcement path in Spain runs through the CNMC and through the courts, and it can move faster than Commission DMA proceedings for the purpose of securing interim relief or a specific disclosure order.

For a detailed account of how national-level marketplace proceedings play out in a neighboring EU jurisdiction, see our anonymized account of resolving a German marketplace suspension.

Step 4: Run the DSA statement-of-reasons challenge in parallel

If the self-preferencing conduct includes or is accompanied by a specific listing restriction – a content moderation decision, a listing removal, or a visibility reduction that qualifies as a restriction on service – the DSA provides a separate, faster procedural track. Amazon, as a Very Large Online Platform (VLOP) under the DSA, must provide a statement of reasons for any such restriction. The seller has the right to use Amazon's internal complaint-handling mechanism to challenge that statement, and if dissatisfied, to refer the matter to an out-of-court dispute settlement body certified under the DSA.

The DSA track is not a substitute for the DMA self-preferencing complaint. It addresses a different legal obligation. But it can produce a concrete remedial outcome – reinstatement of a listing, reversal of a restriction – faster than a Commission investigation into structural self-preferencing, which can take months to years to reach a formal conclusion. In matters we handle, running both tracks in parallel is often the right strategy: the DSA challenge addresses the immediate commercial damage, while the DMA complaint builds the record for the longer structural remedy.

The practical challenge is keeping the two tracks coherent. The arguments made in a DSA challenge should not contradict the evidence assembled for the DMA complaint. The timeline of events should be consistent across both filings. The entity receiving each complaint – Amazon's internal system for DSA, the Commission or CNMC for DMA – is different, but Amazon will have visibility across both. That visibility argues for precision and consistency from the first document filed.

Step 5: The seller's decision points and trade-offs

At the end of Step 4, a seller on Amazon ES faces a set of choices that depend on where the matter stands. If the internal complaint produced a substantive Amazon response that partially addresses the ranking issue, the question is whether that response is adequate and verifiable. Platforms sometimes adjust ranking parameters quietly in response to a well-framed complaint without formally acknowledging doing so. That outcome – real but undocumented – may satisfy the seller's commercial need but does not protect against recurrence. Documenting the post-complaint pattern for several additional weeks is the sensible discipline.

If the internal complaint produced a non-response or a templated denial, the escalation decision is: Commission complaint alone, CNMC complaint alone, or both simultaneously. The trade-off is transparency versus speed. A Commission complaint is public in the sense that it becomes part of the Commission's docket, and Amazon will eventually be aware of the specific submission. A CNMC complaint under national competition law may move faster to an interim measure but has a narrower remedial scope. In our practice, the decision turns on the severity of the ongoing commercial harm – if the harm is material and ongoing, interim relief from a national authority may be more urgent than the structural remedy a DMA proceeding can eventually deliver.

The second major decision point concerns DSA out-of-court settlement. DSA-certified dispute settlement bodies can provide a faster resolution for specific listing restrictions. The body's decision is not binding on Amazon in the same way a court order is, but platforms in practice respond to adverse DSA settlement outcomes – partly because the DMA and DSA are now under active Commission scrutiny, and adverse patterns in settlement outcomes become data points in enforcement investigations.

The third decision point is whether to pursue private litigation in parallel. The DMA does not create a private right of action directly in EU courts in the way the Lanham Act does in the US. However, national competition law – including Spanish competition law enforced through the CNMC and the Spanish courts – can support a damages claim if the self-preferencing conduct caused quantifiable loss. That track is longer and more expensive, but for a seller with documented multi-year harm, it may be the only path to compensation rather than merely behavioral change.

The myth that EU sellers have no leverage once a platform acts against them does not hold up against the actual procedural architecture of the DMA, DSA, and P2B Regulation. What is true is that leverage is procedural – it depends on filing in the right sequence, maintaining a consistent evidentiary record, and understanding which instrument produces which kind of remedy. Sellers who treat these as documentation exercises rather than legal proceedings tend to exhaust their options before they have fully used them.

For sellers navigating parallel EU obligations – particularly where questions about UK marketplace treatment post-Brexit intersect with ongoing EU proceedings – the practical checklist in our guide to UK marketplace suspension after Brexit addresses the cross-jurisdictional sequencing issues that arise most often.

Where does this go wrong?

The most common failure mode is treating the DMA complaint as an internal Amazon ticket. Sellers send a message through Seller Central's standard support channel, receive a non-response, and conclude the process is futile. It is not futile – but the standard support channel is not the DMA internal complaint mechanism. Amazon's DMA-compliant internal system is a separate pathway, and reaching it requires knowing where to look and how to frame the submission.

A second failure is timing. The DMA does not set a short-stop limitation period for complaints to the Commission in the way some national claims are time-limited, but delay matters for a different reason: evidence degrades. Algorithm behavior changes. The Buy Box pattern that was systematic for three months last fall may look different by the time a seller gets around to filing a complaint in the spring. Evidence gathered in real time is always stronger than evidence reconstructed from memory or incomplete exports.

A third failure involves inconsistency between parallel filings. A seller who argues one set of facts to Amazon's internal system and a slightly different set of facts to the Commission creates a contradiction that weakens both proceedings. Disciplined documentation from Step 1 – the same dataset, the same timeline, the same articulation of harm – prevents this.

A fourth and structurally important failure is conflating the DMA self-preferencing issue with an Amazon performance or policy suspension. These require different responses on different timelines through different channels. A seller who is simultaneously dealing with an account health issue and a DMA self-preferencing pattern needs to keep those tracks strictly separate. Mixing the two – trying to raise the DMA issue in a Plan of Action, for instance – almost always produces a worse outcome on both fronts.

We regularly see matters where a seller's first instinct was correct – the Buy Box or ranking pattern was real and systematic – but the way the complaint was framed lost the advantage before the escalation step. The DMA gives EU sellers tools that did not exist before designation. Using those tools correctly is a matter of sequence, not just substance.

A home electronics seller on Amazon ES (winter 2026) came to us after repeated Buy Box losses on ASINs where their pricing and fulfillment metrics matched or exceeded Amazon's own retail offer. We reviewed the Seller Central data exports, structured the ranking discrepancy documentation across twelve weeks of consistent pattern, framed and filed the DMA internal complaint with specific reference to the ranking transparency obligations under P2B, and pursued the DSA statement-of-reasons challenge on two ASINs that had been subject to a visibility restriction. The internal complaint produced a substantive Amazon response within several weeks – not an admission, but an explanation of ranking parameters that was more detailed than the standard disclosure. The DSA challenge on the two restricted ASINs produced a reversal of the visibility restriction. The DMA file remains open as a documented record.

Related areas

• EU Marketplace Regulation – DMA, DSA, P2B, and GPSR compliance for EU sellers
• Amazon Account Reinstatement – strategy and drafting for performance and policy deactivations

If the internal Amazon process has not produced an adequate response and you are weighing escalation to the CNMC or the Commission, the framing of the next filing is the critical variable. To get a read on your specific documentation and where the complaint stands procedurally, email info@tutamenlaw.com.

Frequently asked questions

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

The timeline depends on which procedural track produces the resolution. An internal Amazon complaint under the DMA's mandatory internal complaint-handling system may produce a substantive response within several weeks if well-framed and properly escalated. A DSA statement-of-reasons challenge followed by an out-of-court dispute settlement referral can resolve a specific listing restriction in a similar timeframe. A formal Commission investigation into structural self-preferencing is a considerably longer process – DMA enforcement proceedings have run for many months to years. In practice, most Amazon ES sellers pursuing a self-preferencing complaint will see the first substantive movement at the internal complaint or DSA stage, with the Commission filing serving as escalation leverage and a longer-term structural remedy.

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

The primary risk is filing in the wrong procedural channel, which wastes time and can weaken later filings. A second risk is inconsistent evidence across parallel tracks – a statement made to Amazon's internal system that conflicts with what is later submitted to the Commission or CNMC. A third risk is conflating the DMA complaint with a standard Amazon support ticket or account health issue, which routes the matter to seller support and produces no DMA-relevant outcome. Sellers also frequently underestimate the documentation burden: the Commission and national authorities expect structured evidence of the pattern, not a narrative. Acting without awareness of the P2B ranking transparency obligations and the DSA statement-of-reasons mechanism means leaving two procedural tools unused.

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

There is no legal requirement to retain a lawyer to file a DMA complaint with the European Commission or the CNMC. However, the practical answer is that the quality of the initial filing determines a great deal of what is possible later. A DMA complaint that identifies the correct gatekeeper obligation, presents evidence in the format that regulators expect, and sequences the internal complaint and escalation steps correctly is a substantively different document from an unassisted seller ticket. In matters we handle, early attorney involvement at the documentation and internal complaint stage routinely produces better outcomes than retaining counsel after an inadequate first filing has already been submitted and responded to. For sellers with material ongoing commercial harm – significant Buy Box losses, systematic search demotion – attorney-led handling of the complaint from Step 1 is the more efficient path.

If a prior DMA internal complaint or DSA challenge has already come back without a satisfactory result, a second review can identify the specific gap in the framing and assess whether escalation to the CNMC or Commission is the right next move. Email info@tutamenlaw.com with a summary of what was filed and what response was received.

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. We engage EU regulation matters through DMA, DSA, P2B, and national competition channels – and for matters requiring local filing in a jurisdiction outside our direct surfaces, we work with appropriate local counsel. To discuss your situation, email info@tutamenlaw.com.

By Dmitri Aronov – Partner, EU Marketplace Regulation, Tutamen. August 20, 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.