There’s no specific notice requirement for wage cuts under Ontario ESA. Accordingly, the required notice depends on what your contract and HR policies say. If they don’t specify a notice requirement, look to organization practices and notice you customarily provide employees of changes to employment terms. At a minimum, I think employees should get notice of one pay period, although two would be better. Also be careful that your cut doesn’t violate minimum wage requirements or give rise to claims of constructive dismissal keeping in mind that courts and arbitrators are apt to see big cuts, e.g., 20% or more, as crossing the constructive dismissal line.