What is a solicitor's undertaking and how can it save a closing that would otherwise fail?

A solicitor's undertaking is a formal promise, given by one lawyer to another, to do something specific, such as registering a document, obtaining and registering a mortgage discharge, or providing a missing piece of paperwork, usually within a defined short period after closing. Because Ontario lawyers face serious professional consequences for breaking an undertaking, other lawyers are willing to rely on one as if the promised task were already done, which is what makes it useful.

This matters on closing day because it lets deals proceed despite a loose end that cannot realistically be tied up in the moment, such as a registry outage, a discharge statement that has not yet arrived from a lender, or a document requiring a signature that is delayed by a few hours. Rather than stopping the whole transaction, the lawyers agree the closing will proceed on the basis that the outstanding item will be completed shortly afterward, on the strength of the undertaking. If the undertaking is not fulfilled, the lawyer who gave it faces potential discipline, which is generally enough incentive for undertakings to be honoured even when circumstances get complicated.