In the context of the legal profession in England and Wales, a promise by a solicitor to do, or to refrain from doing, a certain act. A solicitor's undertaking must be given either by a solicitor or on behalf of a solicitor or solicitors' firm (an authorised body).

As a solicitor will be expected to comply with the undertaking according to its terms, within a reasonable time, the undertaking should only be given if it is within the solicitor’s control to perform the act required by the undertaking.

Breach of a solicitor's undertaking is a matter of professional misconduct. Depending on the specific circumstances, a breach may also give rise to other consequences such as breach of contract or breach of trust.

For information on solicitors' undertakings and the legal and regulatory issues which arise when giving a solicitor's undertaking, see Practice note, Solicitors' undertakings: legal and regulatory considerations for solicitors and law firms. For a checklist summarising points to consider before giving a solicitor's undertaking, see Checklist, Solicitors' undertakings. For more information on the court's jurisdiction to enforce solicitors' undertakings, see Article, Enforcing solicitors’ undertakings: practical implications of the Supreme Court’s decision in Harcus Sinclair v Your Lawyers [2021] UKSC 32.