Senior NHS executives have been told to stop paying interim senior staff off payroll to tackle possible tax avoidance.
The letter, written by NHS chief executive Sir David Nicholson, was leaked to the Health Service Journal. It says that in special circumstances, off-payroll payments may be used for up to six months.
It states that if a temporary worker earning more than £220 a day is off the NHS payroll for more than six months, they will need to provide assurances that they pay income tax and National Insurance.
Trusts should "terminate the contract if the assurance is not provided," said HSJ.