The details were contained in the Commissioner's report released today.
A total of 115 complaints were made to the Irish Language Commissioner in 2014.
The annual report shows that in Donegal an investigation found that the Health Service Executive failed to comply with the statutory language obligations whilst communicating with parents and guardians of primary school pupils in the Donegal Gaeltacht in respect of dental services.
Elsewhere, a Government Department had to overhaul its system for issuing cheques - after it put Chinese letters into someone's name where there should have been fadas instead.
The report reveals how one public body had to change the Irish signage on a van - because the Irish text written on it was wrong.
A separate public body also had to re-issue a letter to customers after the original version had been translated from English to Irish using a faulty online translation tool.
As part of its monitoring process, phone calls were made at different times to the main offices of local
authorities, during work hours and after work hours.
Donegal and Laois County Councils were the only authorities that were using recorded oral announcements which were in compliance with the Regulations.