Accountable care systems and accountable care organisations

Authors: Tom Moberly 

Publication date:  06 Sep 2017

Sustainability and transformation partnerships are evolving into these new organisations, which will have responsibility for all NHS and social care. Tom Moberly explains what this means

What are accountable care systems and accountable care organisations?

In an accountable care system (ACS) several healthcare organisations agree to provide all health and social care for a given population. An accountable care organisation (ACO) is a body that manages the agreements to establish such a system and is accountable for all care. Distinctions between the two terms are often overlooked, and they are sometimes used interchangeably.

How did the terms originate?

Accountable care organisations began in the US, with groups of healthcare providers coming together to provide care for a given population. Examples include the Group Health Cooperative of Puget Sound, Washington State; the Geisinger Health System, western Pennsylvania; and Intermountain Healthcare in Salt Lake City.[1] ACOs are accountable to patients and funders for care that meets particular quality metrics within set costs, often based on a capitation funding model. For some time, ACOs have been suggested as a way to help the UK improve integration of health and social care providers.

How are they likely to function in the NHS?

In the English NHS, ACSs are being established as a new phase in the development of sustainability and transformation partnerships (STPs). In June, Simon Stevens, NHS England’s chief executive, told delegates at the NHS Confederation conference that eight of the most advanced STPs in England would be the first to evolve into ACSs. One of these areas is Greater Manchester, which last year took control of its £6bn (€6.5bn; $7.8bn) health and social care budget in a historic devolution of power.[2] These ACSs will integrate funding for, and be responsible for delivery of, all health and social care within a geographical area. All STPs should become ACSs over the next few years, but it is expected to be several years before the ACSs formally become ACOs.

How do they relate to existing NHS structures?

The 2012 Health and Social Care Act established clinical commissioning groups (CCGs), which replaced primary care trusts in England in 2013. In 2014, Stevens published the Five Year Forward View, a plan to save the NHS in England £22bn a year. Stevens argued that these savings were necessary to help close the widening gap between funding and demand for services. In 2015, 44 STPs (partnerships between CCGs, NHS trusts, and local authorities) were announced to develop plans to implement the Five Year Forward View at local level. These STPs are expected to evolve into ACSs to deliver the savings envisaged.

Will they supersede other NHS structures?

An ACS will ultimately supersede the STP from which it is formed. It is also likely that, to increase efficiency and reduce costs, they will subsume the functions of some other NHS bodies, such as CCGs. However, many of the organisations founded after the 2012 act, including CCGs, were established on a statutory basis. Legislation would be needed for ACSs to replace organisations such as CCGs. However, with the government focused on Brexit negotiations, there is unlikely to be parliamentary time over the next 18 months to develop such legislation.

Who are their proponents?

Stevens says that transforming STPs into ACSs will integrate funding and delivery, and that they will effectively dissolve the boundaries between commissioners and providers that have existed since an internal market was introduced into the NHS in 1990. “We are now embarked on the biggest national move to integrating care of any major Western country,” Stevens said at the June conference. “For patients this means better joined up services in place of what has often been a fragmented system that passes people from pillar to post.”

What do critics say?

Critics, such as east London GP Youssef El-Gingihy, say that having a capped budget for each area will increase cost control by denying services to patients, especially because ACSs will be responsible for the £22bn a year savings for the NHS in England.[3] In a statement on ACSs, the BMA said it “has repeatedly called for government and NHS leaders to ensure proper governance structures are in place before changing structures.” The BMA thinks that the necessary legislative changes “are unlikely to happen” under a minority Conservative government and that this leaves “serious governance issues.”


  1. Shortell S, Addicott R, Walsh N, Ham C. Accountable care organisations in the United States and England Testing, evaluating and learning what works. King’s Fund, 2014. [Link]
  2. Vize R. The Greater Manchester experiment. BMJ  2016;352:i1611. [Link]   [Link] .
  3. El-Gingihy Y. The choice is between US-style private health insurance under a Theresa May dystopia, and a public NHS under Jeremy Corbyn’s progressive vision. Independent 2017 Jun 2. [Link]

Tom Moberly UK editor, The BMJ

Cite this as BMJ Careers ; doi: