How often does an Ontario corporation have to update its individuals-with-significant-control register?

The individuals-with-significant-control register isn't something an Ontario corporation can set up once and forget. The Business Corporations Act requires it to be kept current on an ongoing basis, meaning the corporation needs to update it whenever it becomes aware of a change affecting who qualifies as an ISC or what information about an existing ISC is recorded — a share transfer that changes control, a new shareholder crossing the threshold, or a change to an ISC's recorded details, for example.

On top of updating for specific changes as they happen, corporations are also expected to take reasonable steps at least annually to confirm the register is accurate and to identify any changes that might not have been reported to them directly, rather than relying entirely on shareholders to volunteer updates.

In practice, this means building a habit of reviewing the register whenever share ownership changes, a shareholders' agreement is amended, or a new investor comes in, and treating an annual check as a baseline even if nothing appears to have changed. Waiting until a transaction or a regulator's request forces a review is exactly the situation this ongoing obligation is meant to prevent.