€13.4 million is owed to the hospitals in the west and northwest by private health insurance companies due to the failure of consultants to sign off on invoices.
Details about monies owed were given to the HSE West's Regional Health Forum in Galway this afternoon.
The overall figures outstanding are said to be consistent with other hospital groups around the country. €7.7m of the total due is owed to Galway University Hospital.
The Health Service Executive says almost €6m of outstanding fees are owed for less than 60 days.
The hospital group's Chief Operating Officer, Tony Canavan, said efforts had been made to speed up the process of collecting money from health insurance companies in recent years.
Mr Canavan said there had been changes to the way in which claims were processed, including the fast-tracking of documentation by private health insurance holders. He said a significant focus was being placed on the need to collect income.
On a related issue, the meeting heard that over €2.4 million was gathered in car parking fees from visitors to Galway University Hospital between 2011 and 2013.
Around €120,000 of this total was paid to the car park operator in management fees. Mr Canavan said every other cent was put back into patient care.
Responding to claims by Councillor Pádraig Conneely that car park charges amounted to a "tax on the sick", Mr Canavan said the system in place was fair.
He said it was important to manage the scarce resource of parking spaces in an affordable and balanced manner.
The meeting has also heard criticism about the chief executive of the HSE West North West Hospital Group for his role in the awarding of a contract to the former chair of the group board.
Noel Daly resigned as chair earlier this month after controversy about his shareholding in a company that drew up a report into the provision of maternity services at five hospitals in counties Galway, Mayo, Sligo and Donegal.
The contract - worth €20,000 - did not go to tender, in what was a breach of HSE financial regulations. Yesterday the review into maternity services across the group was abandoned.
Group CEO Bill Maher did not respond to calls for his resignation at this afternoon's meeting.
His position was described as "untenable" by Cllr Conneely, who said a report costing €20,000 was now being binned, as a result of the problems that arose from the way in which the contract was awarded.
The meeting was also informed that Mr Daly received €28,000 in travel expenses during his time in office. His took on the role as chair of the board in a voluntary capacity.
At the start of the meeting, Fianna Fáil Councillor Tom McNamara from Co Clare was elected to succeed Cllr Conneely as chair of the forum.