Is a formal passing of accounts mandatory whenever an estate has a minor beneficiary in Ontario?

Not automatically in every case, but a minor beneficiary changes the practical picture significantly. The usual shortcut — beneficiaries reviewing an informal accounting and signing a release accepting it — doesn't work the same way for a minor, because a child generally can't give a legally binding release the way an adult beneficiary can. That gap is exactly what makes formal, court-supervised passing of accounts far more likely to be needed, or at least expected, whenever a minor has a financial interest in the estate.

In practice, where a minor's share is involved, oversight bodies that protect minors' interests in estate matters are often engaged, and a formal passing of accounts becomes the more reliable way to get the accounting properly approved and to protect the trustee going forward, rather than relying on an informal release that the minor legally couldn't have given anyway.

Because the right approach depends on the size of the minor's interest and the estate's specific circumstances, an estate trustee dealing with a minor beneficiary shouldn't assume an informal accounting will be sufficient, and should get advice early on whether a formal passing, or another protective mechanism, is the appropriate route for that beneficiary's share.