A troubled overhaul of a payroll and HR system for police is on track to go live in September.

Police had aimed to have a new Human Resources Management Information System running last month, but that date has been pushed out until September.

Its whole-of-life budget has blown out by about $8 million and will now be up to $64 million.

The project's difficulties are outlined in a Treasury briefing to Finance Minister Bill English last year, obtained by Labour under the Official Information Act.


"The consortium has significantly underestimated the resource required to deliver the project, particularly the police resource that they need to call on," the briefing states.

Stuart Nash, Labour's police spokesman, said police had a history of delayed IT projects, with close to half of current projects late in 2014/15.

"Police have got no money. The burglary resolution rate is below 10 per cent ... operational costs are going through the roof in terms of salaries," Mr Nash said.

"They can't afford what is happening with this. It has become unaffordable ... we are not talking about a super-wealthy ministry here with a lot of cash to burn. Two million buys a lot of resource in downtown Auckland, in Hawkes Bay, in Wellington and all these places."

The Treasury is monitoring the HRMIS as part of its work overseeing the Government's 38 riskiest projects, which total $20.5 billion.

Superintendent Mike Johnson said the HRMIS system was expected to go live in September.

"This is, however, a complex project and our focus is on ensuring that we get it right. Accordingly, the timeframe and the budget for this project have been revised as the project has developed, which reflects its complexity."

Mr Johnson said the budget had been reforecast from the original budget of $56.2 million to $64 million.

A $2 million "burn rate" referred to in the Treasury documents was estimated before this reforecast, and was no longer valid.

"There is a robust governance programme in place for this project, which includes closely monitoring costs. Police will advise the Government should any budget issues arise."

In February, Commissioner of Police Mike Bush appeared before Parliament's Law and Order Committee and said the payroll overhaul was a very challenging and complex piece of work. Any cost increase would be met from within the existing police baseline.

The police payroll system is the latest Government IT project to experience problems.

The Education Ministry's Novopay payroll system led to widespread pay errors for school staff.

Eventually taken over by the Government, it cost an extra $45 million.

Technical changes to implement child support reforms also cost tens of millions of dollars more than originally estimated, while efforts to merge the computer systems of Customs and the Ministry for Primary Industries are almost $30 million over the initial budget.

Treasury documents released to media dated August, September and November 2015, there is reference to a $2 million per month "project burn rate", if the April date go-live were to slip.

This was previous to the budget reforecast and revised project delivery date of September 2016, and subsequent approval from Cabinet to increase total life cost to $64m, from $56.2m.