Mr Rickards revealed this week he received a $300,000 payout.
He left the force in November last year, effectively halting internal police disciplinary action against him.
He and two former police officers Bob Schollum and Brad Shipton were acquitted in 2006 of historic charges of raping Louise Nicholas 20 years ago during the 1980s.
An Ombudsman's report shows police could have paid out Mr Rickards $130,000 -- based on three months' notice -- if they had specified a "limited notice period" in his contract, the Weekend Herald reported today.
But because there was no such clause, Mr Rickards was able to claim $300,000 based on the 13 months remaining in his five-year fixed contract.
Chief Ombudsman Beverley Wakem was critical of the absence of such a clause, which she said contributed to the public-interest argument that details of the settlement be made public.
"My understanding is that fixed-term employment agreements in the public sector should incorporate measures -- such as limited-notice periods -- to minimise the exposure of the agency to large liabilities in the event of early termination, Ms Wakem says in her report. "I have reviewed Mr Rickards' employment contract, and I have not identified any such provision.
"If, as a result, he is entitled to a payment equivalent to 13 months' salary, then there is a very substantial public interest in the police being publicly accountable for this situation and the financial exposure that has resulted."
Police general manager of human resources Wayne Annan said Mr Rickards did have a requirement in his contract to give at least three months' notice of resignation but it was not limited and he gave 13 months' notice effectively the balance of his five-year contract.
Police had a choice between pursuing the disciplinary process, during which Mr Rickards would have continued to be paid and to accrue leave entitlements, or reaching an agreement.
Mr Annan said the disciplinary charges were brought under a system where a judicial process based on district court rules applied. This was prone to delay and open to appeal, and there was no guarantee it would be completed within the 13 months, so a decision was made to pay out Mr Rickards' contract.
The police internal disciplinary regime has been overhauled since charges against Mr Rickards were brought. The new process was expected to be quicker.
Mr Rickards, who is now seeking admission as a lawyer, had been suspended on full pay for three years while awaiting trial and the $300,000 brought his total payout to $750,000.
He was granted a certificate of good character by the New Zealand Law Society this month, effectively clearing the way for him to become a lawyer.
West Auckland urban Maori organisation Waipareira Trust said it was negotiating with Mr Rickards for him to take a part time job aimed at reducing the crime rate among Maori youth.
