A referendum on whether to have four-year fixed parliamentary terms in Queensland has officially passed, with the state's Electoral Commission (ECQ) declaring the vote.

Of the 80 per cent of ballots counted, 51 per cent of voters favoured the change compared to 46 per cent who opposed it.

The informal vote for the March 19 poll was 3 per cent.

Legislation will be introduced to Queensland Parliament that will change the current three-year variable terms to a fixed date, the last Saturday of October, every four years.

The four-year terms will not apply until after the next state election.

"The result showed that there was broad support across the majority of state electoral districts for the move from three-year flexible to fixed four-year parliamentary terms," the ECQ said in a statement.

"The Electoral Commissioner will officially return the writ for the referendum to the Governor of Queensland in the next week."

Those supporting the 'Yes' case argued it would reduce the cost of elections, give more certainty for businesses, and encourage jobs and investment in the Queensland economy.

It is the first referendum passed in Queensland since 1910, when the public supported religious instruction in schools.