What happens when parents with joint decision-making can't agree on a major decision?

When parents share joint decision-making and cannot agree on a major decision, the matter must be resolved — neither parent can simply proceed unilaterally without risking a breach of the court order or agreement.

Many separation agreements include a dispute resolution process for exactly this situation: first, the parents must attempt direct negotiation; if that fails, they go to mediation with an agreed mediator before either can bring a court motion. This process keeps costs down and avoids using court as a first resort.

If dispute resolution fails or no process is set out, either parent can bring a motion to the Ontario Superior Court of Justice (Family Court) asking a judge to make the specific decision. The judge applies the best interests of the child test and can make the decision or direct the parties toward a particular outcome.

In high-conflict cases where joint decision-making consistently breaks down, a court may eventually vary the arrangement to give one parent sole authority over certain categories — for example, sole educational decision-making — to avoid ongoing litigation.