The Mental Health Bill [HL] is a government bill that would amend the Mental Health Act 1983. The 1983 act is the current legislation that regulates the compulsory detention and treatment of those with a mental disorder in England and Wales. There have long been calls to update the legislation, and in 2017 there was an independent review of the Mental Health Act. In 2022 the previous Conservative government published a draft Mental Health Bill. The current bill is similar (but not identical) to the draft bill and it would implement many of the recommendations of the 2017 independent review. Changes proposed in the bill include tightening the detention criteria in the 1983 act and providing for more frequents reviews; limiting the period that people with autism or a learning disability can be detained; and removing prisons and police stations as “places of safety” in the act. This briefing provides a summary of the background to the bill, the bill’s provisions, and the differences from the 2022 draft bill.