IT Release Schedule

Details of proposed changes to IESO systems and reports being revised for the current release are available here. Each release includes a preliminary, target and final planposted according to the IT Release Schedule. A yellow box indicates that the plan is not published for this release.

Target Release Plan

Final Release Plan

Release

Release ID R54.1  R55.0 R55.1 R56.0 R56.1
Release Category Category 2 Category 3
(incl. Cat 2)
Category 2 Category 3
(incl. Cat 2)
Category 2
Real Time Production Build 3 Dec 2025 4 Mar 2026 3 Jun 2026 9 Sep 2026 2 Dec 2026
1. Preliminary Release Plan Prepared 20 Aug 2025 19 Nov 2025 18 Feb 2026 27 May 2026 19 Aug 2026
2. Market Participant Feedback Period Ends 3 Sep 2025 3 Dec 2025 4 Mar 2026 10 Jun 2026 2 Sep 2026
3. Target Release Plan 17 Sep 2025 17 Dec 2025 18 Mar 2026 24 Jun 2026 16 Sep 2026
4. Final Release Plan 15 Oct 2025 14 Jan 2026 15 Apr 2026 22 Jul 2026 14 Oct 2026
5. Sandbox Implementation 23 Oct 2025 22 Jan 2026 23 Apr 2026 30 Jul 2026 22 Oct 2026
6(a). Production Build
(Non Real Time)
26 Nov 2025 25 Feb 2026 27 May 2026 2 Sep 2026 25 Nov 2026
6(b). Production Build
(Real Time)
3 Dec 2025 4 Mar 2026 3 Jun 2026 9 Sep 2026 2 Dec 2026

Four times per year, the IESO schedules a Preliminary Release Plan detailing upcoming changes to IESO systems that have been assessed to have an impact on participants. Comments on IT changes in the plan can be sent to pending.changes@ieso.ca. Each release includes a preliminary, target and final plan, categorized as the following:

  • Category 3 releases (occurring twice a year) require market participants to make changes to their own technical interfaces with the IESO. Normally, significant system changes are the subject of stakeholder consultation well in advance of this release process.
  • Category 2 releases (occurring four times a year) require market participants to make a change in procedure or to update documentation, but not to modify any IT systems.
  • Category 1 releases do not have any impact on market participants and are managed through the IESO's internal release process. Market participants are notified only of any applicable outages, via the Planned IT Outages webpage.

Updates to the Preliminary Plan are added to the Target Release Plan, which is also open for comment by participants. New items are added to the Target Release Plan if required, and are posted through the IT Release Schedule.

The Final Release Plan is published one week in advance of the Sandbox implementation date, when changes are made available in the Sandbox environment for testing and training. Participants can contact IESO Customer Relations for more information if Sandbox access is required.

After the testing period is complete, the IESO will release the changes in Production, as shown on the IT Release Schedule. Accompanying documentation for the changes is available on Pending Changes – Documents as part of the baseline process.