March 2023 

Morningstar Indexes Recalculation 

Guidelines
Morningstar Indexes Recalculation Guidelines | March 2023

2 ©2023 Morningstar, Inc. All rights reserved. The Morningstar name and logo are registered marks of Morningstar, Inc. Marks 

used in conjunction with Morningstar products or services are the property of Morningstar or its subsidiaries.

Contents

Overview ...........................................................................................................................................................................3

Index Recalculation Policy ................................................................................................................................................3

Handling of Corporate Action Errors and Defects That Do Not Affect the Index Weighting Factor...................................4

Index Restatement Process ...............................................................................................................................................4

Exceptions .........................................................................................................................................................................4

Approval and Review.........................................................................................................................................................5

About Morningstar Indexes...............................................................................................................................................6
Morningstar Indexes Recalculation Guidelines | March 2023

3 ©2023 Morningstar, Inc. All rights reserved. The Morningstar name and logo are registered marks of Morningstar, Inc. Marks 

used in conjunction with Morningstar products or services are the property of Morningstar or its subsidiaries.

Overview

Morningstar Indexes strives to deliver the highest-quality data. However, inaccuracies may occur, and Morningstar Indexes 

retains the right to recalculate and restate an index when one of the following events has occurred:

• Missed or late announcement of a corporate event. 

• Error in closing price of constituent securities.

• Dividend error.

• Missed or incorrectly applied data input.

• Incorrect application of methodology.

• Index calculation error.

This document explains the index recalculation process that Morningstar Indexes follows. A set of well-defined guidelines 

leads to predictable outcomes, ensures that index recalculations are put through consistent internal procedures, and complies

with the industry’s voluntary standards, such as the International Organization of Securities Commissions Principles for 

Financial Benchmarks (IOSCO Principles) and UK & EU Benchmark Regulation.

Index Recalculation Policy

In general, index calculation data input defects—such as price, dividends, or foreign-exchange rates, that do not affect the 

index weighting factor—if discovered within two trading days, are corrected, and the index is recalculated regardless of the 

performance impact. Such errors discovered after two trading days typically only result in an index restatement if the impact 

on performance is material; otherwise, they are corrected prospectively. Errors involving mandatory corporate actions will 

generally be corrected with a restatement, regardless of the performance impact. 

For all other errors that affect the index weighting factor, Morningstar Indexes will escalate the issue to the Morningstar 

Index Operations Committee. The Index Operations Committee considers regulatory requirements, the information originally 

available to clients, whether the error caused the index to deviate from its stated objectives, as well as impact on performance 

and clients. Morningstar Indexes may correct the error prospectively, providing two days’ advance notice where possible;

issue a restatement; or take no action. 

If a real-time value or end-of-day values are restated for indexes that publish intraday values, Morningstar Indexes will not 

recalculate real-time values. Only the end-of-day values will be restated. 

Incorrect identifiers are generally discovered on the day of the error. Corrections will be included in the next scheduled file 

delivery.

Errors discovered in the back-testing of an index after the go-live date can be corrected without consulting with the Index 

Operations Committee, provided they are limited to index calculation data input defects that do not affect the index weighting 

factor. Back-test errors involving incorrect methodology application or data input errors affecting composition or weight will 

be escalated to the Index Operations Committee.
Morningstar Indexes Recalculation Guidelines | March 2023

4 ©2023 Morningstar, Inc. All rights reserved. The Morningstar name and logo are registered marks of Morningstar, Inc. Marks 

used in conjunction with Morningstar products or services are the property of Morningstar or its subsidiaries.

Please note that the above guidelines are the standard approach and apply to all asset classes of indexes. Any occurrence of 

an unprecedented error type will be assessed case by case by the Index Operations Committee. In all cases, decisions that 

differ from the stated process will be reviewed and announced accordingly by Morningstar Indexes.

The Operations Committee will report to Compliance and the Morningstar Index Oversight Committee at least quarterly on 

restatements including incident reports with details on causes and associated remedial actions. 

Handling of Corporate Action Errors and Defects That Do Not Affect the Index Weighting Factor 

The table below outlines Morningstar Indexes' standard approach for handling corporate action errors, as well as index 

calculation data input defects that do not affect the index weighting factor:

Event Approach

Missed or late announcement 

of mandatory corporate actions

Mandatory corporate actions, such as stock splits, bonus issues, or stock 

dividends and reverse stock splits, are corrected on the appropriate ex-date, and 

the index will be recalculated.

Error in closing price of 

constituent securities

Closing prices are corrected. The index and affected multi-asset indexes will be 

recalculated.

Dividend error Incorrect or missed dividends are corrected on the appropriate ex-date, and the 

index and affected multi-asset indexes will be recalculated. Canceled dividends, 

if already applied, may be proactively reversed before the pay date. 

Missed or misapplied data 

input

If it is determined that performance and/or portfolio composition is materially 

affected, the index and multi-asset indexes will typically be recalculated.

Incorrect application of 

methodology

If it is determined that the index methodology was incorrectly applied, the index 

and multi-asset indexes may be recalculated or corrected prospectively.

Index calculation error If it is determined that there was a material error in index calculation that does 

not affect the index weighting factor, the index and multi-asset indexes will 

generally be recalculated. Such errors that do affect the index weighting factor 

may result in a recalculation or prospective correction.

Index Restatement Process

In case of restatements, Morningstar Indexes will review the issue upon detection and restate within a reasonable time 

frame. If an index is restated, the following steps will be completed:

• Morningstar Indexes will regenerate and repost all affected files.

• Morningstar Indexes will notify all affected clients of the restatement and file reposts once the process is completed.

Exceptions

While Morningstar will seek to apply the method described above as a standard, the market environment, supervisory, legal, 

financial, or tax reasons may require an alternative approach to be adopted in certain instances. A decision to take an 

alternative approach will be made by the Morningstar Index Operations Committee solely; or, where appropriate, by the 

Morningstar Index Operations Committee in conjunction with the relevant Morningstar Methodology Committee. In all 

instances, the application of a non-standard process will be reported to the Morningstar Index Oversight Committee. 
Morningstar Indexes Recalculation Guidelines | March 2023

5 ©2023 Morningstar, Inc. All rights reserved. The Morningstar name and logo are registered marks of Morningstar, Inc. Marks 

used in conjunction with Morningstar products or services are the property of Morningstar or its subsidiaries.

Approval and Review 

This document is reviewed by Morningstar Index Operations Committee at least annually or as required, if there are any 

relevant changes to applicable law or regulation. The Morningstar Index Oversight Committee is responsible for approving this 

policy and any subsequent amendments.
Morningstar Indexes Recalculation Guidelines | March 2023

6 ©2023 Morningstar, Inc. All rights reserved. The Morningstar name and logo are registered marks of Morningstar, Inc. Marks 

used in conjunction with Morningstar products or services are the property of Morningstar or its subsidiaries.

About Morningstar Indexes

Morningstar Indexes was built to keep up with the evolving needs of investors—and to be a leading-edge advocate for them. 

Our rich heritage as a transparent, investor-focused leader in data and research uniquely equips us to support individuals, 

institutions, wealth managers, and advisors in navigating investment opportunities across major asset classes, styles, and 

strategies. From traditional benchmarks and unique IP-driven indexes to index design, calculation, and distribution services, 

our solutions span an investment landscape as diverse as investors themselves. 

Morningstar Index Methodology Committee

The Morningstar Index Methodology Committee oversees all new index development, index methodology changes, and 

cessation of indexes for any indexes where Morningstar owns the intellectual property. This committee is also charged with 

ensuring that indexes align with Morningstar Research principles and values. The group comprises members of the index 

team with index research, product development, product management, client service, index implementation, and operation 

expertise who provide the first layer of governance over index design and methodology. 

Morningstar Index Services Methodology & Administration Committee

The purpose of the Morningstar Index Services Methodology & Administration Committee is to oversee all new index

development, index methodology changes, and cessation of indexes for any indexes where Morningstar provides calculation 

and administration services but does not own the Intellectual Property of the indexes. The group is comprised of members of 

the index team with index research, product development, product management, client service, index implementation and 

operation expertise who provide the first layer of governance over the index calculation services and administration business, 

with regard to index design and methodology.

Morningstar Indexes Operations Committee

The Morningstar Index Operations Committee governs the processes, systems, and exception handling of the day-to-day 

management of all live indexes, including index rebalancing and reconstitution, restatements, market classification, and 

contingency management. The committee oversees the annual review of index methodology (as required by U.K. and EU 

benchmark regulations, or BMR), ensuring that methodologies remain fit for purpose and continue to achieve their stated 

investment objectives. The group comprises members of the index team with data, operations, corporate actions, product 

development, index launch, client service, and index management experience who provide the first layer of governance over 

index operations. 

Morningstar Index Oversight Committee

The Morningstar Index Oversight Committee is responsible for the index oversight function as per the requirements of the U.K.

and European BMR, providing independent oversight of all aspects of the governance of benchmark administration as 

required by the relevant BMR. Its remit extends to all calculation and administration-related business activities of Morningstar 

Indexes, including administration of Morningstar-owned benchmarks as well as client-owned benchmarks and index 

calculation. The oversight function is part of the organizational structure of Morningstar but is separate and independent from 

the index business, index management, and the other index committees.

www.indexes.morningstar.com

Contact Us

indexes@morningstar.com

The information in this document is the property of Morningstar, Inc. Reproduction or transcription by any means, in whole or part, without the prior written consent of 

Morningstar, Inc., is prohibited. While data contained in this report are gathered from reliable sources, accuracy and completeness cannot be guaranteed. All data, 
Morningstar Indexes Recalculation Guidelines | March 2023

7 ©2023 Morningstar, Inc. All rights reserved. The Morningstar name and logo are registered marks of Morningstar, Inc. Marks 

used in conjunction with Morningstar products or services are the property of Morningstar or its subsidiaries.

information, and opinions are subject to change without notice. This document may contain back-tested or simulated performances, and the subsequent results achieved by 

the investment strategy may be materially different.