The stock exchange's disciplinary tribunal has publicly censured Diligent and fined it $100,000 for failing to file financial accounts through 2013, in three successive reporting periods.
Diligent, which provides software for corporate boards, told NZX in August last year that it had been recognising revenue incorrectly and that it would have to re-state its financial accounts for the previous three years.
That also meant Diligent wasn't able to provide the required financial reports for the rest of 2013 by the deadlines.
As well, it several times failed to meet its own guidance for when it would produce these reports.
The company did not provide its preliminary and final half-year reports for the six months ended June 2013 until 28 February this year, five and six months late.
Diligent also failed to present its annual report for calendar 2013 by the end of March, finally producing it on 30 April.
NZX's disciplinary tribunal says it considers these failures to report on time to be very serious.
During the six months it took Diligent to correct its significant accounting error, investors continued to trade its shares without the benefit of all the information they were entitled to under NZX rules.
The tribunal says the reporting requirements are fundamental to the integrity of the share market.