Victorians are voting early and by postal votes in record-breaking numbers, a surge which could see more than 1 million votes cast in the state election before polling booths open on Saturday.

The boom in early voting means that if seats are very tight at the finish of counting on Saturday night, and if the overall seat tally is on a knife-edge, a clear election result may not be known until next week.

Early votes will not be counted on election night. Instead, the counting of early votes will start on Monday.

As of 4.50pm Tuesday, a staggering 467,368 early votes had been issued, roughly 200,000 more than at the same point during the 2010 state election campaign. The total number of early votes at the 2010 poll, 543,000, was itself a record and double the number at the 2006 election.

In addition to the early vote surge, 97,684 postal votes had been returned to the Victorian Electoral Commission as of 4.50pm Tuesday. So that's 565,052 votes so far, representing 14.86 per cent of enrolled voters.

The number of postal votes will climb steadily in the lead-up to polling day, and then climb slowly next week. As of Monday afternoon, the VEC had processed 321,000 applications for a postal vote.

Paul Thornton-Smith, an information officer with the VEC, confirmed the surge in early voting, adding that it was on track to be "significantly more than last time." Asked if the combined tally of early votes and postal votes could exceed 1 million, he said: "I would say it's possible, yeah."

If the combined tally exceeds 1 million, it would mean that more than one in four voters on the electoral roll would have voted before polling day. There are 3,806,301 eligible voters on the roll.

Mr Thornton-Smith said the VEC was prepared for the increase in early voting and could move staff around to help with counting. "If the overall election result is really close and it looks as if it could be down to one or two districts, we'd put extra resources into those," he said.

"With a very large number of votes that can't be counted until after election day, if the overall election result is very close, you won't know on election night who's won. But I guess there's nothing very unusual in Australian elections about that," he said.

"We basically predicted there'd be a 30 per cent increase [in early voting], which would bring it up to 700,000. Now for the first few days of the election the numbers were way above that, even up to 100 per cent above what they were at the same time last time. It seems to be levelling out a bit now," he said.

Counting of the early votes would be completed "within a very few days" after polling day, Mr Thornton-Smith said.

Nick Economou, senior lecturer in politics at Monash University, said it had been long observed in Australian politics that postal votes favoured the conservative vote. But he said there was no evidence that early votes favoured either side of politics. "My recollection (of the 2010 state election) is that the counting of the pre-poll votes didn't really change the results anywhere," he said.