He will appear in the North Shore District Court in January next year.
The officer was stood down in April once the criminal investigation started.
There is also a parallel employment investigation, as well as a separate inquiry by the Independent Police Conduct Authority.
The complainant, who now lives in Australia, was the victim in a serious domestic violence prosecution the officer investigated 15 years ago.
The woman filed a formal complaint with the IPCA in April which alleged the officer became a "bit too friendly"; buying her flowers, asking her out for dinner and giving her a nickname.
"He asked me out for dinner and wanted me to wear a red or black dress. I declined and felt a bit weird about it. He then arrived at the house with wine and pizza."
Even though the woman, who was in her mid 20s, began to feel "uncomfortable with the situation" she said she felt pressured to engage with him as he was dealing with the case against her partner.
In her IPCA complaint, the woman described several alleged sexual encounters.
"I didn't know what to say or do so just lay there scared and in shock."
The IPCA is also investigating a leaked letter, revealed by the Herald, in which a police whistleblower warned bosses about an alleged sex scandal involving the officer.
The letter was sent to Northland district commander Superintendent Russell Le Prou in November 2016, but the officer was not questioned about the anonymous allegation.
The sex allegation was one paragraph in a five-page letter, without any times or dates or the name of any complainant, said police in response to previous Herald inquiries.
"Police considered that this single paragraph (a vague comment via two anonymous sources) did not provide a basis upon which to launch an investigation.
"No further information was forthcoming which altered that view."
But the letter was also not forwarded to the IPCA, even after an official investigation was launched in April, until the Herald revealed its existence.
