But it said there was not enough "cogent" evidence to criminally charge the officer, who denied the allegation.
The investigation started in May 2018 and was not finished until August 2020.
Police would not comment on any specifics - not even which year or which district this occurred in - because they said it was an employment matter.
When asked by RNZ about the delay in the investigation, the consequences for the officer, and the discrepancy between the policy breach and lack of criminal charges, a statement from police's media team said:
"The matter referred to in the IPCA summary was reported to Police in February 2018.
"As this is an employment matter, Police will not be providing any further comment or information.
"However, in response to your second question, it is important to note that a matter can be a breach of an employment policy without being a criminal offence."