Tory ministers face anger after admitting NHS staff are still paying up-front to use the NHS - and many will face waiting wait six months for a refund.
Boris Johnson vowed in May to exempt migrant workers in the NHS or care system from the £624-a-year Immigration Health Surcharge.
He later pledged health and care workers who had already paid the fee would be refunded, backdated to March 31.
But health leaders say workers are still having to make up-front payments.
And the government today confirmed some will be unable to start getting refunds until at least October 1, with future refunds paid in six-monthly reimbursements.
The delay applies to migrant health and care workers who will not be eligible for the new Health and Care Visa - such as those who joined family in the UK, or came via a youth mobility scheme.
It's thought they will need to show they've remained in a health or care job for six months, and receive payments in six-monthly reimbursements.
Those who come to the UK on the new Health and Care Visa after it launches will be exempt at the point they apply.
Migrant workers on the current Tier 2 'skilled worker' visas, meanwhile, have already started getting refunds "and this process will continue", the Home Office said.
The Royal College of Nursing blasted the policy - which comes after weeks of demands for up-front payments to end.
General Secretary Dame Donna Kinnair said: "We have waited for weeks for this update from the Government.
"[We] are disappointed with the news that many staff - particularly those working in social care - will still have to pay this grossly unfair financial charge upfront in order to work in the UK.
“The proposed system of reimbursement for these workers does not go far enough.
"They must be reimbursed immediately in full to compensate for the initial, unjust financial burden imposed.
"The Government is running out of time to resolve the issues facing the social care sector.
"If they continue to ignore the warning signs, health and care services across the UK will be put at risk, as will the care of patients and those supported by social care."
The Immigration Health Surcharge is an annual fee to use the NHS which is charged to most workers from outside the European Economic Area.
It will be hiked from £400 to £624 in October and is due to extend to millions of EU nationals living in the UK from 2021.
The government today said the exemption for health and care staff will be permanent beyond the coronavirus crisis.
And Health Secretary Matt Hancock pledged "all employees working in health and social care" would be exempt.
A government statement confirmed: "As part of the launch of the Health and Care Visa, those who apply via the visa and their dependants will be exempt from the Immigration Health Surcharge.
"The Government has already began refunding Immigration Health Surcharge payments for any healthcare professionals on Tier 2 visas who have paid since 31 March 2020, and this process will continue.
"The Department of Health and Social Care is currently working with the sector to set up operational arrangements for reimbursing health and social care staff outside the scope of the Health and Care visa.
"These arrangements will commence from 1 October in six-month reimbursements."
