The new police payroll system has been pushed out to go live in April, after testing revealed "complexities" around integration with other systems.
Police's Human Resources Management Information System (HRMIS) is replacing the current ageing payroll system after a bungle left NZ Police owing more than $40 million to its staff.
The problems have been ongoing since 2009, and relate to entitlements under the Holidays Act 2003.
The new system is expected to make it easier for people to manager HR information such as pay, learning, leave, time and personal information.
It will also provide a workforce management system that supports modern policing, and IT tools to help with the mobile nature of police work.
The solution itself is built, but additional time is needed for testing and ensuring that staff are trained and ready to use the new system.
The major vendor, PwC, brought in an international team with experience in implementing these types of solutions.
The project will be reassessed and a revised plan developed, so the system will be able to go live in April.
Police would not say how much the delay would cost.
"Commercial negotiations are ongoing between parties and therefore police cannot comment as these are negotiations are commercially sensitive," a spokesperson said.
Superintendent Mike Johnson said the project was always going to be a complex one, and both police and PwC were focused on getting it right.
"Police is a large 24/7 organisation with over 12,000 employees," he said.
"We have complex scheduling and industrial requirement and challenges were always likely with a project of this nature.
"The revised time frame will allow time to address the issues raised through testing and ensure our people are well prepared to maximise the benefits of the new system.
"We have always said that the top priority was a system that meets our needs and pays our people correctly from day one of operation," he said.
"Testing has highlighted some complexities around integration with other systems."
PwC have brought on an international SAP specialist who has validated the work already done and revised the delivery plan, said PwC partner and consulting leader Paul Nickels.
"We are making positive progress in ongoing commercial discussions, which we envisage will be resolved in the coming weeks."