Self‑preferencing on Marketplaces in Turkey 2026: TCA Enforcement, Risks & a Compliance Checklist

Self‑preferencing on platforms in Turkey has moved from a theoretical concern to an active enforcement priority for the Turkish Competition Authority (TCA). Throughout 2024–2026, the TCA has signalled, through landmark decisions, binding commitments and formal policy proposals, that digital marketplaces favouring their own products or services over those of third‑party sellers will face escalating scrutiny. For in‑house counsel and compliance teams operating e‑commerce platforms in or into Turkey, the risk calculus has shifted: the question is no longer whether the TCA will intervene, but how quickly your platform can demonstrate marketplace neutrality. This article provides a practical compliance playbook, from the legal tests that trigger liability, through the evidence investigators request, to a ready‑to‑implement 10‑step prevention checklist.

TL;DR, six immediate compliance actions:

• Audit your ranking algorithm for any parameter that systematically advantages own‑brand or affiliated listings.
• Establish discovery‑ready logging, retain search‑ranking logs, click‑through data and promotional algorithm versions for a minimum of five years.
• Insert non‑discrimination clauses into seller agreements and internal product‑launch protocols.
• Separate commercial and marketplace functions so that teams managing the platform do not share competitively sensitive seller data with own‑retail units.
• Create an incident‑response playbook for TCA information requests, including an external‑counsel trigger point.
• Benchmark against the Trendyol commitments, they now serve as a de facto compliance standard for every Turkish marketplace.

What the TCA Means by Self‑Preferencing

Under Turkish competition law, self‑preferencing describes conduct by a vertically integrated platform that systematically favours its own products, services or affiliated offerings over those of competing third‑party sellers who rely on the same platform to reach consumers. The TCA frames this conduct within the abuse‑of‑dominance prohibition set out in Article 6 of Law No. 4054 on the Protection of Competition. Article 6 prohibits undertakings holding a dominant position in a relevant market from engaging in exploitative or exclusionary practices, and the TCA has explicitly treated self‑preferencing as a species of exclusionary abuse.

In practical terms, the Turkish Competition Authority has identified several recurring forms of self‑preferencing on digital platforms:

• Ranking bias. Algorithmically boosting own‑brand or affiliated listings in search results, category pages or recommendation carousels, irrespective of relevance, price or consumer preference signals.
• Privileged data access. Allowing internal retail or logistics teams to use aggregated seller data (sales volumes, pricing trends, inventory levels) that is not available to competing sellers on the platform.
• Preferential promotional placement. Reserving premium advertising slots, homepage banners or “deal of the day” positions for own products without offering equivalent access to third parties on comparable commercial terms.
• Discriminatory pricing or fee structures. Imposing higher commission rates, fulfilment fees or listing charges on third‑party sellers while exempting own‑brand products from equivalent costs.

Industry observers expect the TCA to continue expanding its catalogue of recognised self‑preferencing conduct types as digital business models evolve, particularly in areas such as logistics integration and payment‑gateway steering.

When Does Self‑Preferencing Become an Abuse?

Not every instance of a platform featuring its own products constitutes an infringement. The TCA applies a structured assessment rooted in dominance, foreclosure and proportionality. Understanding these thresholds is essential for self‑preferencing platforms in Turkey that wish to draw the line between lawful commercial strategy and prohibited conduct.

Establishing market power

The first step in any TCA investigation is defining the relevant market and assessing whether the platform holds a dominant position. For marketplace operators, this typically involves a two‑sided market analysis: the platform‑to‑consumer side and the platform‑to‑seller side. The TCA examines market shares, barriers to entry (network effects, data advantages, switching costs) and the degree of seller dependence on the platform for consumer access. Where a marketplace accounts for a significant share of online retail traffic in a product category and sellers have limited alternative routes to market, dominance is readily established.

Foreclosure risk and exclusionary effect

Once dominance is found, the TCA assesses whether the self‑preferencing conduct produces or is capable of producing an exclusionary effect, that is, whether it restricts, distorts or prevents competition by rival sellers or rival platforms. Two analytical hypotheses recur in TCA practice:

• Hypothesis 1, dominant platform plus internal product favouritism. The platform operates both as a neutral marketplace and as a direct retailer. By steering demand toward its own retail arm through algorithmic advantages, it forecloses competing sellers who cannot replicate those advantages.
• Hypothesis 2, hybrid platform leveraging data and logistics. The platform uses its privileged access to seller data or its integrated logistics infrastructure to develop competing products or to offer delivery advantages that independent sellers structurally cannot match.

The TCA does not require proof that foreclosure has already materialised; a demonstrated capability to foreclose, supported by evidence of systematic conduct, is sufficient. The likely practical effect is that platforms with market shares exceeding 40 per cent on either the seller or consumer side of the marketplace will face the most intense scrutiny, though the TCA has not published a formal safe harbour.

Evidence and Indicators the TCA Uses in Self‑Preferencing Investigations

TCA investigations into self‑preferencing are data‑intensive. Enforcement teams request granular digital evidence, and platforms that cannot produce it face adverse inferences. The table below maps the principal evidence types, their significance, and what compliance teams should preserve.

Early indications suggest that the TCA is also beginning to request algorithmic explainability documentation, internal reports or technical specifications that describe, in non‑code terms, how the ranking system makes decisions. Platforms that invest in explainability now will be better positioned to respond to information requests without triggering extended investigation timelines.

Trendyol Decision and Commitments, Lessons for Self‑Preferencing Platforms in Turkey

The TCA’s investigation into Trendyol, one of Turkey’s largest e‑commerce marketplaces, stands as the leading enforcement precedent for self‑preferencing in the Turkish market. The investigation examined allegations that Trendyol systematically favoured its own retail operations and affiliated logistics services over third‑party sellers on its platform.

The case was resolved through binding commitments proposed by Trendyol and accepted by the TCA Board. While the full reasoned decision text is maintained on the TCA’s official portal, the key commitments, as summarised in detailed analyses published by leading Turkish competition practices, establish a practical benchmark that every marketplace operator should treat as a minimum compliance standard:

• Equal treatment in search rankings. Trendyol committed to ensuring that its ranking algorithms do not systematically prioritise own‑brand or affiliated listings over third‑party products based on seller identity.
• Data portability and access. The commitments addressed data‑sharing asymmetries by requiring that third‑party sellers receive meaningful access to their own performance and transaction data, and that internal retail teams do not exploit aggregated seller intelligence.
• Non‑discriminatory logistics access. Where Trendyol offered integrated fulfilment services, the commitments required that third‑party logistics providers and self‑fulfilled sellers not be disadvantaged in ranking or visibility.
• Monitoring and reporting. Trendyol accepted ongoing monitoring obligations, including periodic compliance reports to the TCA.

The practical lesson is clear: the TCA will use the Trendyol commitments as a template when assessing other platforms. Industry observers expect future enforcement actions to reference these commitments as an established standard, making proactive alignment a strategic imperative rather than a discretionary choice.

Practical Compliance: Algorithm, Contracts and Operational Controls

Reducing TCA enforcement risk requires coordinated action across three domains: technical systems (algorithms), legal instruments (contracts) and organisational design (operational controls). The following framework distinguishes between quick fixes that compliance teams can implement within 30 days and longer‑term structural changes.

Algorithm governance, quick fixes

• Neutral default ranking. Remove any ranking parameter that directly or indirectly references seller identity (e.g., “is_own_brand” flags, “platform_fulfilled” boosts that apply exclusively to own logistics). Replace with consumer‑relevance signals: price competitiveness, review scores, delivery speed and stock availability.
• A/B test controls. Require that all A/B tests involving ranking changes are logged, time‑stamped and approved by a compliance officer before deployment.
• Explainability documentation. Produce a plain‑language summary of the ranking algorithm’s key decision factors, updated with each material change, and store it in a compliance repository accessible to external counsel.

Algorithm governance, longer‑term structural measures

• Third‑party audit programme. Engage an independent technical auditor to review ranking outcomes annually, comparing own‑brand vs. third‑party performance at equivalent relevance scores.
• Algorithm versioning and rollback capability. Implement full version control for ranking models, enabling the compliance team to identify precisely which algorithm was live on any given date and to roll back problematic changes.

Contractual clauses for marketplace neutrality

Seller agreements and internal policies should include explicit non‑discrimination provisions. Sample clause elements for digital platforms compliance include:

• “The Platform shall not use any ranking parameter that systematically advantages products sold by the Platform’s own retail division or affiliated entities over those of third‑party sellers, except where the parameter is based on objective, verifiable consumer‑relevance criteria applied equally to all sellers.”
• “Third‑party sellers shall have access to their own transaction data, including sales volumes, return rates and customer review aggregates, through the Platform’s standard reporting tools, on terms no less favourable than those available to the Platform’s internal retail teams.”
• “Promotional placements shall be allocated through transparent criteria published in the Seller Handbook. Own‑brand products shall participate in the same allocation process and on the same commercial terms as third‑party products.”

Operational controls, information barriers

• Data‑access separation. Implement role‑based access controls ensuring that employees in the platform’s own‑retail division cannot access aggregated third‑party seller data (pricing intelligence, demand forecasts, inventory levels).
• Internal product‑launch protocol. Require a documented competition‑law review before launching any own‑brand product in a category where third‑party sellers are active on the platform. The review should assess whether the launch relies on insights derived from seller data and whether the product will receive any ranking or promotional advantage.
• Compliance officer sign‑off. Designate a senior compliance officer with authority to block or modify algorithm changes, promotional campaigns or contract terms that present self‑preferencing risk.

A 10‑Step TCA Response and Prevention Checklist

The following checklist is designed for legal and compliance teams at marketplaces operating in Turkey. Each step includes an estimated implementation effort to help prioritise resource allocation.

1. Appoint a TCA response lead. Designate a senior lawyer or compliance officer as the single point of contact for all TCA communications. Effort: Low.
2. Activate discovery‑ready logging. Ensure ranking algorithm logs, click‑through data, pricing records and data‑access audit trails are being retained in a forensically sound manner for at least five years. Effort: Medium.
3. Conduct a baseline algorithm audit. Review current ranking parameters for any factor that directly or indirectly favours own‑brand listings. Document findings and remediation steps. Effort: Medium.
4. Implement information barriers. Restrict internal retail teams’ access to aggregated third‑party seller data through technical access controls and updated employment policies. Effort: Medium–High.
5. Update seller agreements. Insert non‑discrimination and data‑access clauses aligned with the Trendyol commitment benchmarks. Effort: Medium.
6. Establish an A/B test governance protocol. Require compliance sign‑off for ranking experiments, with automatic logging and rollback capability. Effort: Medium.
7. Publish a promotional‑placement policy. Create transparent, non‑discriminatory criteria for banner ads, deal pages and “best seller” badges, available to all sellers. Effort: Low–Medium.
8. Schedule annual third‑party ranking audits. Engage an independent technical auditor to benchmark own‑brand vs. third‑party listing performance. Effort: High (recurring).
9. Draft a TCA information‑request response playbook. Prepare template responses, document‑hold notices and internal escalation procedures so the team can respond within the TCA’s typical deadlines. Effort: Low–Medium.
10. Train commercial and product teams. Deliver annual competition‑law training tailored to marketplace operations, covering self‑preferencing risks, data‑handling rules and escalation triggers. Effort: Low (recurring).

If you receive a TCA information request:

• Issue an immediate document‑preservation notice across all relevant business units.
• Notify your TCA response lead and external Turkish competition counsel within 24 hours.
• Map the data flows requested against your existing logging infrastructure and identify any gaps.
• Do not alter, delete or overwrite any algorithm version, log file or internal communication that falls within the scope of the request.
• Prepare a privilege log for any documents withheld on legal‑privilege grounds.

Turkey (TCA) vs EU DMA, a Comparison for Self‑Preferencing Platforms

Platforms operating across both Turkey and the European Union must navigate two distinct but increasingly convergent regulatory frameworks. The table below highlights the key differences and similarities that matter for digital platforms compliance and platform algorithm compliance strategies.

The key distinction for compliance teams is that the TCA’s framework is enforcement‑driven: obligations crystallise through decisions and commitments rather than through pre‑set rules. This means that the scope of prohibited self‑preferencing conduct in Turkey is defined retroactively through case law, creating uncertainty that only proactive compliance can mitigate. Platforms already subject to the EU DMA will find that DMA‑compliant practices substantially reduce TCA risk, but a Turkey‑specific compliance layer, addressing local market definitions, TCA evidentiary expectations and commitment benchmarks, remains essential.

Conclusion: Priorities for Self‑Preferencing Platforms in Turkey

The TCA’s enforcement trajectory is unambiguous: self‑preferencing on digital marketplaces is a priority target, and the Trendyol commitments have established a practical compliance floor that every platform operating in Turkey should treat as a minimum standard. The regulatory direction, toward greater marketplace neutrality, data‑access parity and algorithmic transparency, is unlikely to reverse.

Compliance teams should act now on three fronts. First, conduct a baseline algorithm audit to identify and remediate ranking parameters that advantage own‑brand listings. Second, update seller agreements and internal policies to reflect the non‑discrimination and data‑access standards embedded in the Trendyol commitments. Third, build a TCA response capability, logging infrastructure, preservation protocols and external counsel relationships, before an information request arrives.

For platforms operating across multiple jurisdictions, coordinating Turkish compliance with EU DMA obligations offers efficiency gains, but the differences in regulatory architecture mean that a bespoke Turkish strategy is indispensable. Businesses seeking guidance on TCA enforcement risk and digital platforms compliance can explore further resources through our practical guide to commercial law disputes in Turkey or connect with specialists through the Turkey lawyer directory.

Sources

1. Turkish Competition Authority (Rekabet Kurumu)
2. ELIG Gürkaynak, Self‑Preferencing in Turkish Competition Law
3. Mondaq, Trendyol Commitments on Self‑Preferencing and Data Portability
4. Paksoy, Turkish Competition Law Newsletter 2026
5. Kolcuoğlu, TCA Proposals on E‑Commerce Platforms
6. European Commission, Digital Markets Act
7. Wolters Kluwer, Turkish DMA: What’s in the Package?
8. Bruegel, Implementing Self‑Preferencing Bans (Policy Paper)
9. EconStor, Competition Policy and Self‑Preferencing (Academic Analysis)