The 33% rule for prisoners came into effect from 1 October 2026. It reduces the length of time that serving prisoners will be held in custody. It has been designed to relieve the burden on UK prisons which are suffering from an overcrowding crisis: the Prison Reform Trust estimated that in 2024-25 almost three-quarters (72%) of prisons were overcrowded leading to safety risks, strains on prison staff and delays to prisoner rehabilitation.
A major change to the law
For decades, most people given a custodial sentence would spend half (50%) of their total sentence in prison and the other half ‘on licence’, i.e. under the supervision of a probation officer who monitored their reintegration into the community. In September 2024, as a response to the immediate prison crisis, the government implemented a temporary emergency policy to reduce the time most inmates spent in prison to 40% of their sentence.
A further reduction under the 33% rule of the Sentencing Act 2026 marks a significant change to law. The new system works as follows:
- The first 33% – this is the minimum time that all prisoners given custodial sentences must serve in prison;
- The second 33% – the prisoner is then released on strict conditions, usually electronically tagged, and given curfews and mandatory appointments with probation. Any reoffending or breaching of their licence conditions is likely to lead to recall to prison, where they will serve out the remainder of their sentence.
- The final 33% – supervision is scaled back for lower risk offenders, but they remain on licence and can be recalled during this period if they breach their conditions or reoffend.
What offences are excluded from the 33% rule?
The 33% rule for prisoners does not apply to certain sentences where the offence is deemed too serious. Any prisoner who receives a life sentence will not be eligible for the 33% rule, nor will those who are convicted of manslaughter*, serious sexual offences and sexual offences against children, or serious violence or terrorism offences (to name just a few). These sentences will continue to be subject to the 50% or often two-thirds (66%) rules.
In August 2026 the government excluded prisoners convicted of manslaughter, who were initially eligible for release under the 33% rule, following public backlash in relation to the unlawful killing of Police Constable (PC) Andrew Harper in 2020. Under the scheme, two of the teenagers convicted of killing PC Harper would have been eligible for release in January 2027.
Staggered release or ‘tranches’ The 33% rule does not mean that all serving prisoners who have completed one-third of their sentence will be released on 1 October 2026. The legislation provides for ‘tranches’ (or stages) allowing prisons to implement the policy and release prisoners in an orderly manner. Prisoners serving shorter sentences who have completed 33% of their sentence will be released in earlier tranches (throughout the remainder of 2026) while those serving longer sentences who have completed 33% will be released in later tranches (up to June 2027).
Any serving prisoner who is unsure about when the 33% rule applies to their sentence should seek clarification from the prison’s Offender Management Unit who will be able to give them a more accurate release date.
How can we help
Our experienced Crime team can support you throughout your case during the police station and court stages or recommend specialist Prison Law firms when necessary.
Contact us for a free, no obligation initial discussion on 020 3440 8000 or email enquiries@tvedwards.com.
Disclaimer: The information on the TV Edwards website is for general information only and reflects the position at the date of publication.
