Jacinda Ardern casts her early vote

Jacinda Ardern is happy with her decision to vote early, joking that she's pretty firm on which way she'll go.

The Labour leader cast her early vote in her Mount Albert electorate on Tuesday morning and is urging others to head to the polls ahead of September 23.

"I've decided. I'm committed enough. I'm locked and loaded and I feel confident about casting my vote," she said ahead of her visit to the ballot box," she said.

She's urging others to get out early and ensure if they're not enrolled they can do so at the time, something that can't be done on election day.

Ms Ardern said thousands voted on election day three years ago but did not have their votes counted because they were not on the electoral roll, something she didn't want to see repeated.

"So really, to make sure there's no room for error, vote early and that'll make sure you're enrolled at the same time," she said.

Early voting, which this year is expected could reach as high as 50 percent, has changed the way the party campaigns, she said.

"Obviously knowing that voting opened on Monday certainly affected that we wanted to get out all of our major policies early," Ms Ardern said.

"But we know we've got to campaign right up until election day. A majority of people are still voting on that day so it's not over until September 23rd breaks."

Ms Ardern wasn't the only familiar face popping out to vote on Tuesday morning.

Former Prime Minister Helen Clark headed along as well, as she'll be out of the country on election day.

She says it's a practice which helps voter turnout.

"I think it's being pushed a lot more this time which is good, because it gives people more of a chance to participate."

NZN / Newshub.