NHS Chief Executive Sir David Nicholson has said he expects the remaining work on the NHS' organisational design to be completed by May.
In a letter to NHS staff following Royal Assent of the Health and Social Care Bill, Sir David said that the future of employees would be confirmed by the end of the year, when the transition will be complete.
But he warned that jobs will undoubtedly be lost by the time new statutory organisations take effect next April.
"The passage of the Bill gives us real clarity and certainty about our future direction,” he said, but “there is an enormous amount to do to prepare for the bulk of the statutory changes”.
In terms of the timetable, the remaining senior appointments will be made within the commissioning structure during May and June. Then, from July to December 2012, the NHS will complete the remaining phases of the transition to ensure new organisations are fully operational from April 2013.
The document outlines a “particular need to retain the skills of certain staff in business critical roles” but admits jobs will be lost with redundancies impacting the budgets of new organisations from 2013/2014. Key milestones for the development of CCGs were also outlined. In July 2012, the first wave of authorisation applications will be accepted – followed by dates in September, October and November.
The NHS Commissioning Board will begin as an Executive Non-Departmental Public Body in October and take on the responsibility for the authorisation of CCGs before it and authorised CCGs take on full statutory powers from April 2013.
In a separate letter released on the same day, Health Secretary Andrew Lansley wrote to NHS staff thanking them for their work during the passage of the Health Bill to Royal Assent.
Mr Lansley said: “The Health and Social Care Act will, in reality, empower NHS clinicians to determine the type of health services needed in their local area, using their clinical expertise and their knowledge to ensure NHS services meet the needs of patients.
“I hope you and your colleagues in the NHS will take advantage of the new freedoms the Act has put in place.”