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.

Preliminary Release Plan

Target Release Plan

Final Release Plan

Release ID

  R 42.1 R 43.0  R 43.1  R 44.0 R 44.1 
Release Category Category 2  Category 3
(Incl. Cat 2)
 Category 2 Category 3
(Incl Cat 2)
 Category 2
Real Time Production Build 4 Dec 2019  4 Mar 2020 3 Jun 2020 16 Sep 2020 2 Dec 2020
1. Preliminary Release Plan
21 Aug 2019  20 Nov 2019 19 Feb 2020 27 May 2020 19 Aug 2020
2. Market Participant Feedback
Period Ends
4 Sep 2019  4 Dec 2019 4 Mar 2020 10 Jun 2020 2 Sep 2020
3. Target Release Plan 18 Sep 2019  18 Dec 2019 18 Mar 2020 24 Jun 2020 16 Sep 2020
4. Final Release Plan 16 Oct 2019  15 Jan 2020 15 Apr 2020 29 Jul 2020 14 Oct 2020
5. Sandbox Implementation 24 Oct 2019  23 Jan 2020 23 Apr 2020 6 Aug 2020 22 Oct 2020
6(a). Production Build
(Non Real Time)
30 Nov 2019  26 Feb 2020 27 May 2020 9 Sep 2020 25 Nov 2020
6(b). Production Build
(Real Time)
4 Dec 2019  4 Mar 2020 3 Jun 2020 16 Sep 2020 2 Dec 2020

See 2019 IT Release Schedule


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 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.