An official audit of garda payroll found evidence that some officers were paid for performing duties at different locations at the same time.
The report also said the health and safety of both officers and the public were placed at “significant risk” because of how many hours some gardaí were working.
It found more than 1,050 cases where a garda had more than 16 hours duty over the course of a continuous 24-hour period.
A case where time and attendance were reported by one person at the Three Arena, on a major garda operation, and for processing files at the same time was also raised in the report.
It said concerns about “the level of work in some cases” had been passed to Garda Internal Affairs and was under investigation.
The audit also listed an astonishing case where an officer had performed 75.25 hours over a period of 80.5 hours. It said “herculean levels of duty” like that were questionable on health and safety grounds.
The findings came from the Garda Internal Audit Service which carried out an examination of garda members who had reported the highest levels of duty.
It detected nine cases where members with a combined total of 124 hours of service were reported to be on duty in two places at the same time.
The report said this was of “significant audit concern” and that the existing manual system of time sheets did not allow for those incidents to be easily discovered.
The audit also found more than 23,000 hours of regular garda duty – the equivalent of 590 working weeks of 39 hours – where the garda member involved was supposed to be on a period of “designated rest”.
It said while “exceptional circumstances” might occur due to garda operations, management were obliged to ensure officers did not breach working time agreements.
Public duties were also performed by officers on annual leave, or time off in lieu (TOIL), in cases covering around 160 hours, the audit found. It said this should not have been happening and that attendance of gardaí should not be required while on holiday or on TOIL.
Garda management said this was not always possible due to the “exigencies of the service” if nobody else was available.
The audit also said non-public duties – relating to football matches, concerts, race meetings, and so on – were performed for 637 hours by officers on designated rest.
Another 85 hours were also listed for non-public duties where the garda was supposed to be on holidays or on time off in lieu.
Garda management said in response that officers could volunteer for such service but were reminded by the auditors that it should not interfere with laws on working time.
The garda audit, which was finalised last November, has been released under FOI and covers the calendar year 2018 when the bill for “extra duty” was an incredible €117 million.
The audit said improvements had since been made but that the findings were a matter of considerable concern. It said the long periods of duty some officers were working were not compliant with EU rules on working time.
It added: “Such incidences represent significant risks specifically relating to: the health, safety, and welfare of personnel of An Garda Síochána, the health, safety, and welfare of members of the public.” The audit also flagged concerns over payment of medical fees for garda members through an in-house scheme to access GPs.
They said this was a “benefit in kind” which was not being taxed and may create a significant liability to the Revenue Commissioners.
A garda spokesman said: “There are policies and procedures in place in An Garda Síochána to ensure that governance is applied in respect of the areas reviewed within the Garda Internal Audit Payroll Report of November 2020.
“In line with those policies and procedures, local garda management are responsible for their budgets and are expected to ensure compliance with approved procedures.” He said the internal audit mechanism provided an additional structure to identify inconsistencies.
“Each discrepancy highlighted is examined individually by local garda management, and appropriate action taken based on the specific circumstances,” he added.