The Health Service Executive has questioned the accuracy and reasonableness of thousands of claims by GPs for out-of-hours care and special services for medical card patients.
RTÉ News has learned that the HSE has sought a "haircut" of around 80% in some cases to claims by GPs for treating patients outside normal hours and providing special services.
The claims go back several years.
In a letter to one GP this month, who has claimed €186,000 in back fees, the HSE has offered a full and final settlement of just €15,000.
A process for dealing with all claims from 2011 up to the end of August was agreed following a recent mediation process involving the Irish Medical Organisation and the HSE.
GPs can accept the HSE offer or appeal it by the end of October.
The HSE said that of settlement offers made to 264 GPs, 225 have so far accepted the payment.
However, the National Association of GPs has criticised the scheme and estimates that as much as €7.5m is owed to up to 200 of its members.
The HSE said it cannot give a full and final figure on the total claimed and total paid out in settlement at this time.
There were 1.6m claims costing €65m in 2011.
Normal surgery hours for GPs with medical card patients are 9am to 5pm Monday to Friday, so out-of-hours claims can only be made outside of these hours.
The claims can only be made where the consultation is urgent and could not be foreseen, and the consultation could not be safely deferred until GP services are routinely available.
GPs are also obliged to ensure all claim forms are completed accurately and fully.
Special items of service provided during out-of-hours consultations attract separate fees.
Among the main special services are vaccination, excisions, suturing of cuts and lacerations, ECG treatments and asthma care.
There were 804,000 out-of-hours claims in 2011, costing the service €34m.
In addition, there were 877,000 special items of service claims, costing €31m.
The Irish Patients' Association has said the HSE should recover the money if any GP is found to have falsely claimed for out-of-hours care fees.
It also said the matter should be referred to the Medical Council.
Stephen McMahon said the money recovered would be new savings in the health budget and should be reinvested in care areas that badly need it.
The IMO said that the majority of GPs are not in dispute with the HSE over payments.
It said that only a small number of doctors have been unable to resolve their difficulties with the HSE, despite protracted efforts to do so.