Changes to the Market Rules, processes, and IT systems that market participants use to interact in the IESO-administered markets, are managed using a clearly defined baseline process. Stakeholder input is sought at critical points throughout the process.

From Idea to Implementation: Making Change Happen

Use this infographic to follow an idea for change through all the stages of the IESO process from engagement to decision making to implementation.  

Changing the Market Rules

The IESO Market Rules define the roles and obligations of market participants and the IESO and set the framework governing the IESO-controlled grid and IESO-administered markets. A series of market manuals and procedures provide more detailed descriptions of requirements and obligations specified in the Market Rules. The IESO Board of Directors has the authority to make and approve the Market Rules. The Ontario Energy Board may be asked to review specific amendments.

On an ongoing basis, proposed changes to the Market Rules are initiated by IESO staff or stakeholders. The IESO uses a consultative process through which individuals with an interest in the operation of the electricity market can request a rule amendment or comment on a rule amendment under consideration.

See Market Rule Amendment Process.

Market Rules & Manuals Library

Market documentation can be accessed from the Market Rules & Manuals Library, which includes the Market Rules, market manuals, procedures, forms, etc. Market rules and related documentation that are undergoing change are flagged.

 Baseline Calendar

The baseline comprises the current set of market documentation including Market Rules, market manuals and other associated documents. A new baseline is issued every quarter reflecting changes in the documents that have been stakeholdered and reviewed using IESO change management processes. The Baseline Calendar outlines a series of proposed timelines for baselines. As these dates approach, they will be confirmed by the IESO through announcements to market participants.

On certain occasions, changes to market documentation will be made to the current baseline to accommodate urgent rule amendments, system changes or IESO procedural changes. These changes will be made on dates other than the baseline dates noted and will be communicated to market participants with as much advance warning as possible. 

Notice of Pending Changes

See Pending Changes for advance notice of changes to the Market Rules, market manuals, technical interfaces, or other items that define the operation of the IESO-administered markets.

Proposed Market Rule Amendments​

Rule amendments currently under consideration by the Technical Panel, or approved by the IESO Board but not yet incorporated into a baseline, are listed at Proposed Market Rule Amendments.

Once an amendment is incorporated into the baseline set of Market Rules, it is included in the Market Rule Amendments Archive.

For history of all market rule amendments, see Market Rule Amendments Archive.

Technical Interfaces & IT Changes

On the Technical Interfaces page, the IESO publishes a series of documents, which detail the requirements and processes for interfacing with IESO technical systems.

IT changes are implemented through a series of scheduled releases, which are published in advance on the IT Release Calendar. Technical Interfaces documentation is available for comment earlier than changes to the market manuals and related documents. The timing of releases is intended to ensure that market participants are given sufficient notice of changes that affect them and an opportunity to provide feedback to the IESO. The IT Release process is explained at Pending IT Services Changes.

Proposed changes to IESO Reports together with the targeted implementation date are listed on Report Listing webpage.

Interpretation Bulletins

Interpretation bulletins are produced by the IESO to provide clarification on the interpretation, application or implementation of a market rule. See current Interpretation Bulletins.


Market participants may seek exemptions from the obligations or standards set out in the Market Rules. The IESO Board of Directors is responsible for making a determination of a market participant's application for an exemption.

See Exemptions for details on the exemption procedure and a list of active exemption applications.