Why does it take so long to count special votes?

Winston Peters has said negotiations to form the next Government won't begin until the election results are official, which isn't until October 7.

Unlike the past few elections where the result has been clear, this one could go either way, it all depending on Mr Peters and New Zealand First.

More than 380,000 people cast a special vote this election, a record. Questions are now being raised as to why it takes so long.