http://www.legislation.gov.uk/ukpga/1983/20/section/21AMental Health Act 1983An Act to consolidate the law relating to mentally disordered persons.1983-05-09texttext/xmlenStatute Law Database2026-04-09Expert Participation2026-04-06 Part II Compulsory Admission to Hospital and Guardianship<Substitution ChangeId="d29p2061" CommentaryRef="c20058921">Duration of authority and discharge</Substitution> Patients who are taken into custody or return within 28 days.21A1This section applies where a patient who is absent without leave is taken into custody under section 18 above, or returns himself to the hospital or place where he ought to be, not later than the end of the period of 28 days beginning with the first day of his absence without leave.2Where the period for which the patient is liable to be detained or subject to guardianship is extended by section 21 above, any examination and report to be made and furnished in respect of the patient under section 20(3) or (6) above may be made and furnished within the period as so extended.3Where the authority for the detention or guardianship of the patient is renewed by virtue of subsection (2) above after the day on which (apart from section 21 above) that authority would have expired, the renewal shall take effect as from that day.4In the case of a community patient, where the period for which the community treatment order is in force is extended by section 21 above, any examination and report to be made and furnished in respect of the patient under section 20A(4) above may be made and furnished within the period as so extended.5Where the community treatment period is extended by virtue of subsection (4) above after the day on which (apart from section 21 above) the order would have ceased to be in force, the extension shall take effect as from that day.S. 21A(4)(5) inserted (3.11.2008) by Mental Health Act 2007 (c. 12), ss. 32, 56, Sch. 3 para. 7 (with Sch. 10); S.I. 2008/1900, art. 2(i) (with art. 3, Sch.)S. 20: cross-heading substituted (3.11.2008) by virtue of Mental Health Act 2007 (c. 12), ss. 32(3), 56 (with Sch. 10); S.I. 2008/1900, art. 2(i) (with art. 3, Sch.)Pt. II (ss. 2–34) modified by Mental Health (Scotland) Act 1984 (c. 36, SIF 85), ss. 17(2), 78(2)Part II (ss. 2-34) modified (E.W.) (1.1.1992) by Criminal Procedure (Insanity and Unfitness to Plead) Act 1991 (c. 25, SIF 39:1), s. 5(1), Sch. 1 para.3 (with saving in s. 8); S.I. 1991/2488, art. 2