UPDATED: 6.09PM Kiwi workers could be in for something of a windfall after the Finance Minister revealed problems with the Holidays Act.

Bill English has revealed the police have paid out $30 million to their staff after entitlements were miscalculated.

The department which administers the Act, MBIE, is now looking at whether 3000 of its employees have been paid correctly.

Mr English said private sector bosses have also spoken to him about the Act.

"This isn't really an issue of lack of competence. It's the complexity of the Holidays Act. Some people have probably been calculating it wrong ever since the Act came in in 2004. I mean, even the police signalled the other day they've gone back 10 years".

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Police Minister Judith Collins said she obviously would have preferred the police to have got it right in the first place.

"When you've got very complex collective agreements where people get something extra every time something happens or there is some sort of clothing allowance, which have been largely done away with in the private sector, it's really complex. We've got to get it right."

Bill English said the Act is complex.

"Employers need to go and check their pay roll systems to make sure they're calculating the holiday pay correctly. It seems to apply, from what we can see in the police anyway, to people who have significant changes in their hours week to week".

Prime Minister John Key agreed it's a complex act and staff are unlikely to have noticed a shortfall.

"If you were overpaid by a significant amount or underpaid by a significant amount, people sort of notice that. But these are very, very small amounts over a long period of time."

But Labour leader Andrew Little said the Government's running true to form, blaming everyone else but itself for having to pay out to public servants because of the Holidays Act misinterpretation.

Little said the Act's been in place for more than a decade.

"The fact that it's taken what, 12 years to get to this point, and one of the largest government departments, the one responsible for administering the Holidays Act, now discovers there's a problem?"