Patients who go abroad for treatment due to long public waiting lists here are facing significant delays in getting reimbursement from the HSE, according to new figures obtained by RTÉ News.
The reimbursement under the EU Cross-Border Healthcare Directive is supposed to be within 30 days but all reimbursements are delayed by at least three months.
The HSE said that there are currently around 2,500 applications to be processed and has apologised for the delays, which it said are due to the volume of claims and manpower issues.
It said that the "normal turnaround time frame to issue a response is now 75 days".
Under the EU Cross-Border Healthcare Directive, patients are entitled to be treated abroad under certain rules and have the cost of their care paid for afterwards by the HSE.
Patients can claim the cost of their treatment abroad up to the amount the treatment would cost in Ireland.
New figures show that the cost of the scheme has increased from close to €2.5 million in 2016, to over €12.2m last year.
The number of claims has also soared from 1,025 in 2016 to 3,886 last year.
The HSE said it is working with the Department of Health to deal with the resourcing of the Cross Border Directive office, to levels which reflect the volume of requests and likely future demands.
Some patients have reported problems in making contact with the main office in Kilkenny.
The HSE said that there are limited telephone lines to the office but this is being addressed and that extra lines will be opened in the coming weeks.
The most common surgeries under the scheme are cataracts, orthopaedic surgeries, gynaecology and general surgery.
The main countries of access are currently Northern Ireland, Wales, the UK in general and Poland.
Patients availing of the scheme need a letter of referral from their GP, or consultant and in some cases, the HSE advises that prior approval be got from HSE.
Recent figures show that over 764,000 people are waiting for public hospital treatment, or to be seen at a clinic here.
The impact of a hard Brexit on patients seeking to access care in Northern Ireland or Britain in future, under the Cross-Border Directive is uncertain.
The HSE has said that some services with Northern Ireland, like paediatric and cancer care, are expected to continue, even with a no-deal Brexit.