The Platts Market-on-Close (MOC) Window

The structured daily auction process through which the world's most important physical oil benchmarks are assessed

The Platts Market-on-Close (MOC) window is the structured daily process through which S&P Global Platts (now formally S&P Global Commodity Insights) determines the daily assessments for Dated Brent, Dubai, Oman, and various other physical crude oil benchmarks. The MOC mechanism is one of the most important institutional features of contemporary oil pricing — the assessments produced through the MOC process feed directly into hundreds of billions of dollars of annual physical crude trade through OSP formulas, derivative contract settlements, and long-term supply agreements. Understanding how the MOC works is essential to understanding the institutional plumbing of contemporary oil markets.

This page covers the MOC window structure, the specific protocols that govern bid, offer, and trade reporting, the methodology by which observed trade activity translates into published assessments, the long-running controversies that have shaped the MOC mechanism, and the role the assessments play in the broader oil market structure.

The Basic MOC Concept

The MOC mechanism is a structured auction window — a defined 30-minute period each business day during which accredited market participants can submit bids and offers for specific physical oil products in standardized form. Platts editorial staff observe and record all bid, offer, and trade activity during the window and use the observed activity to construct the daily published assessment.

The "market-on-close" terminology reflects the timing — the window typically occurs at the end of the relevant regional trading day (4:00-4:30 PM London time for Brent assessment, 4:00-4:30 PM Singapore time for Dubai assessment) — capturing the "closing" market conditions for the day.

The mechanism's purpose is to provide a transparent, verifiable process for daily price discovery in physical crude markets that lack the continuous trading liquidity of exchange-traded futures. The structured window concentrates activity into a defined period that Platts can observe and document comprehensively.

Dated Brent MOC Window

The Dated Brent MOC window operates during a defined 30-minute period at 4:00-4:30 PM London time each business day. The process covers physical crude trade in the BFOET basket (Brent, Forties, Oseberg, Ekofisk, Troll) plus WTI Midland since 2023:

Participants. Accredited market participants include the major oil companies (BP, Shell, ExxonMobil, TotalEnergies, Equinor, Chevron), trading houses (Vitol, Trafigura, Glencore, Mercuria, Gunvor), and other approved entities. Participation requires Platts accreditation that involves credit standing, trading capability, and process adherence requirements.

Bid and offer protocol. Participants submit bids (offers to buy) and offers (offers to sell) for specific cargo sizes (typically 600,000 barrels for Brent-area grades) with specific loading dates and grade specifications. Bids and offers are submitted to Platts editorial staff in real time during the window.

Trade execution. When a bid and offer match (or close enough to support negotiation), trades may execute during the window. Trades are reported to Platts and become part of the data set the editorial staff uses for assessment construction.

Assessment construction. After the window closes, Platts editorial staff construct the daily Dated Brent assessment from the observed bids, offers, trades, and broader market context. The assessment is published shortly after the window closes.

The Dated Brent assessment is one of the most important single numbers in global oil markets, serving as the principal reference for the great majority of Atlantic Basin physical crude trade and as an input to numerous derivative contracts.

Dubai/Oman MOC Window

The Dubai/Oman MOC window operates during a parallel structure during Singapore business hours, with the window typically held 4:00-4:30 PM Singapore time. The process covers physical crude trade in the Dubai assessment basket (Dubai, Oman, Upper Zakum, Al-Shaheen, Murban):

Partials trading. Unlike the full-cargo Brent MOC, the Dubai MOC operates on "partial cargo" basis — typically 25,000-barrel partial cargo units. The smaller unit size reflects the broader participant base and the operational mechanics of the Persian Gulf physical trade.

Multi-grade convergence. The Dubai MOC includes activity across multiple constituent grades, with the assessment construction reflecting the combined activity. The flexibility allows the assessment to reflect available physical supply across the broader Persian Gulf medium sour pool.

Convergence procedures. When sufficient partials accumulate from a single counterparty, they may "converge" into full cargo size, with specific procedural mechanics governing the convergence process.

The Dubai assessment is the principal reference for Middle Eastern crude OSPs to Asian destinations and is one of the most important Asian oil market price discovery mechanisms. For deeper coverage, see our Dubai crude page.

The Assessment Construction Methodology

Platts editorial staff use the observed MOC window activity to construct daily assessments through a process that incorporates:

Observed traded prices. Trades executed during the window provide the most direct price information.

Observed bid and offer spreads. Even without trade execution, bid and offer levels indicate market price discovery.

Quality differentials. Assessment construction accounts for the quality differences among constituent grades within the basket.

Loading date differentials. Different loading dates command different premiums or discounts reflecting market term structure.

Broader market context. Editorial judgment incorporates broader market context including futures market movements, refining margin signals, and other relevant information.

The methodology is published in Platts' methodology documents but ultimately involves substantial editorial judgment that has been the subject of ongoing debate. The combination of structured observation and editorial judgment is the central design feature of the MOC system.

Methodology Controversies

The MOC system has been the subject of substantial controversy across decades:

2006 Brent assessment dispute. Major oil traders publicly disputed Platts methodology changes in the Brent assessment, with various complaints about the impact on physical trade economics.

2013 European Commission investigation. The European Commission opened an investigation into potential manipulation of Brent assessments by major oil companies and trading houses. The investigation was eventually closed without enforcement actions but produced substantial scrutiny of the assessment process.

Various manipulation allegations. Periodic allegations have surfaced about strategic bid/offer placement to move assessments. The allegations have been difficult to verify or refute given the discretionary nature of the assessment process.

2018 Dubai window changes. Methodology changes affecting the convergence procedures in the Dubai MOC produced significant industry debate.

2023 WTI Midland inclusion in Dated Brent. The addition of WTI Midland to the Dated Brent assessment basket was one of the most significant methodology changes in decades, fundamentally changing the underlying physical pool for Brent assessment. The change was implemented after extensive consultation but produced substantial debate about its implications for the benchmark's character.

The controversies have not undermined the MOC system's continued operation but have shaped methodology refinements and regulatory oversight of the assessment process.

The 2023 WTI Midland Inclusion

The 2023 inclusion of WTI Midland in the Dated Brent assessment is worth specific discussion as the most significant single methodology change in the modern MOC era. Background:

Declining BFOET production. The original BFOET production base (Brent, Forties, Oseberg, Ekofisk, Troll) had declined substantially over decades as North Sea production matured. By the early 2020s, BFOET monthly export programs had fallen to levels that raised concerns about benchmark liquidity.

U.S. crude export growth. Post-2015 U.S. crude export ban repeal had produced substantial U.S. light sweet crude (particularly WTI Midland) flowing to Atlantic Basin markets in volumes that exceeded BFOET production.

Assessment integrity questions. Concerns emerged that BFOET physical liquidity alone could no longer support credible benchmark assessment.

Platts proposal and consultation. Platts proposed including WTI Midland in the assessment basket through extensive industry consultation across 2021-2023.

May 2023 implementation. WTI Midland was formally added to the Dated Brent assessment effective May 2023, transforming the benchmark structure.

The implementation has fundamentally changed the underlying physical structure of Dated Brent. The benchmark is no longer purely a North Sea assessment but now incorporates U.S. crude as a substantial physical contribution. The implications for Brent's character as the global oil benchmark have been substantial.

Regulatory Oversight

Following the various controversies, the MOC system operates under regulatory oversight frameworks that have evolved across decades:

IOSCO principles. The International Organization of Securities Commissions has published principles for oil price reporting agencies that establish baseline standards for assessment methodology, governance, and conflict management.

FCA oversight. The U.K. Financial Conduct Authority regulates Platts and other price reporting agencies under U.K. financial regulatory frameworks given the assessments' role in derivative contract settlements.

Internal governance. Platts has progressively strengthened internal governance of the assessment process including separation of editorial functions from commercial operations.

The oversight has not eliminated all controversy but has provided institutional framework for addressing methodology questions and manipulation concerns.

Alternative Assessment Frameworks

The Platts MOC is the principal but not the only oil benchmark assessment system. Major alternatives include:

Argus Media. Provides daily crude and product assessments through alternative methodology approaches. Argus's ASCI methodology (covered in our Argus assessments page) is the principal alternative for U.S. sour crude pricing.

OPIS. Provides various energy market assessments, particularly for refined product markets.

Reuters/ICIS. Various energy market assessments through historical Reuters and Independent Chemical Information Service operations.

The existence of alternative assessment frameworks provides some methodological competition but does not displace Platts MOC as the principal assessment for the major crude benchmarks.

The Platts MOC Window in One Sentence

The Platts Market-on-Close (MOC) window is the structured 30-minute daily auction process through which Platts assesses Dated Brent (London hours) and Dubai/Oman (Singapore hours) — capturing bids, offers, and trades from accredited participants to produce the daily assessments that anchor hundreds of billions of dollars of annual physical crude trade and that have been the subject of recurring methodology controversies including the landmark 2023 inclusion of WTI Midland in the Dated Brent basket.

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