Long wait for postal votes count: AEC

The fate of some federal lower house seats could hang in the balance for two weeks.

The Australian Electoral Commission says it has to wait 13 days from now for all of the postal votes for Saturday's federal election to come back to the home electorates.

"Given it's a close election, we have got to wait for 13 days for all of the postal votes to come back. Really for a couple of the seats, we could be waiting for that period," commissioner Tom Rogers told Seven's Sunrise on Tuesday.

AEC spokesman Phil Diak said the full make-up of the Senate could take four weeks or longer to determine.

"Previous elections show that the Senate can take easily four weeks to complete in some states, sometimes a little more," he told ABC radio.

"The nature of counting is that you need to have all of the votes in the system before you can distribute preferences."

He said the AEC focused on Monday on getting absentee votes back to their home electorates, where they are checked against the electoral role and counted.

"That's a very big logistical exercise and it involves hundreds of thousands of votes."