Just 64.9 per cent of Northlanders under 25 were enrolled. Others would not receive papers if they had moved recently. Ms Cosgrove moved from Wellington to Whangarei in July.
Alex Wright, who was standing for WDC's Hikurangi-Coastal ward, said she was turned away when she went to cast her vote in the Forum North ballot box on Tuesday, despite it stating on her voting pack that papers could be hand delivered.
Ms Wright said a staff member told her the box may overflow if everyone put their votes in it.
"I was told that unless it was a special vote I could not put my voting paper in the ballot box," she said.
WDC chief executive Rob Forlong issued a statement yesterday in response to both incidents, outlining the special voting process.
"Unfortunately, voting in the local government elections follows a more complicated process if you aren't on the Electoral Roll," he said.
"At this stage of the voting period we are encouraging people to post their votes rather than putting them in the ballot box. This way they get to our electoral officer faster which means they contribute to our voter return statistics and assist with an earlier result on election day."
Voter turnout had been steadily falling since the 1980s.
As of yesterday, 21 per cent of eligible voters in Whangarei had returned their votes, compared to 20.6 per cent at the same point in the 2013 election.
In the Far North, 22.35 per cent had voted so far, compared to 25.3 per cent in 2013. In Kaipara, the figures were 23.72 per cent compared to 17.1 per cent in 2013, though last election Kaipara residents were not electing district councillors, only voting for NRC and DHB members.
Anyone who had not received voting papers in the mail needs to:
1. Update their details on the electoral roll: Visit a post shop, phone 0800 36 76 56, visit elections.org.nz or free text your name and address to 3676.
AND
2. Cast a special vote: Call 0800 922 822 (before October 5) or visit your nearest council office. Locations at localelections.co.nz/vote.