A visit to hospital could require patients packing their passports under proposed government guidelines.
Guidance has been issued to hospital trusts across the country to ensure visitors prove British citizenship.
The move is said to be a clampdown on so-called health tourism; foreign nationals flying into the UK to use the NHS.
And it could save the health service up to £500m a year by 2017/18, according to reports.
Speaking to a national newspaper, Roger Goss of pressure group Patient Concern, said: “It’s a worthwhile price to pay to attempt to recover the tens of millions owed by health tourists.
“If it is successful, the money recouped could be invested in better care for those patients who are entitled to it for free.”
Measures to screen patients for eligibility include forms in outpatient and A&E wards asking them for their passport number, nationality, GP name and NHS number and health bodies could impose fines for any lapses.
In February, the Department of Health was reportedly set to introduce a pilot scheme to test the feasibility of GPs asking their patients for proof they are eligible for free NHS care, with doctors asked to identify patients who should be paying for the treatment they receive.
An official study in 2013 estimated that £388 million is spent each year on patients in England who should already be paying for their care but are not being charged by the NHS. It said just 16 per cent of costs are being recovered.
It added that the cost of people who come to England with the purpose of getting free treatment on the NHS could be anywhere between £70m and £300m.
Mike Pye, interim director of finance at Wrightington, Wigan and Leigh NHS Foundation Trust, told the Evening Post: “WWL has established major milestones in adhering to legal obligations to identify overseas visitors and carry out robust and reasonable residency checks in order for to determine eligibility for free NHS treatment.”