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.
It is one of 709 complaints made to the office of the Irish Language Commissioner last year, outlined in its annual report.
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.
Elsewhere, the report reveals that all but two of Ireland's local authorities are breaking the law by not having Irish versions of their recorded telephone messages.
The report says that amongst the most significant complaints received were 40 regarding the Road Safety Authority (RSA) and 17 in relation to Irish Water.
There were also three complaints each received about the National Car Testing Service (NCT), the Teaching Council and the Property Services Regulatory Authority.
There was a slight increase in the number of new complaints - from 702 in 2013 to 709 in 2014.