A new single-test subsidy will come in from July 2, increasing payments for most people receiving childcare payments by as much as $1333 a year for the average child.

But submissions from childcare organisations to a parliamentary red tape committee suggest the new subsidy won't reduce complexity but will create new problems for both providers and families.

Three weeks before changes are due to be introduced, nearly a third of families eligible for the increased payments haven't transitioned to the new system by updating their details on myGov.

The Community Child Care Association says the system was designed to be simpler than the current multi-payment system.

"CCC considers this a missed opportunity to remove red tape and ensure families had equal access to a less complex system," a submission from the organisation says.

They claim the test - which links fortnightly parent hours of study, work or volunteering, averaged over three months to the number of care hours subsidised - is "an unnecessary burden on families and services".

It's a claim backed by Australian Community Children's Services.

That organisation claims it will make managing enrolment lists more complex for services.

Parents could also struggle to maintain consistent access to child care and face difficulty managing the reporting requirements.

The changes include rebates targeted towards families working, looking for work, studying or volunteering.

Means-tested rebates would also see low-income earners receiving up to an 85 per cent subsidy for their childcare costs compared with 72 per cent previously.

Federal Education Minister Simon Birmingham says 800,000 families have made the switch, but more than 1.1 million families could be eligible.

He expects around 230,000 people will increase their workforce participation as a result.

"For some that will be choosing to work more hours or more days, for others that will be choosing to go back to work for the first time ever," he told ABC radio.

HOW AVERAGE AUSTRALIAN FAMILIES WILL BENEFIT:

* A family on $50,000 - both parent/s working, with two children aged under 6 in long day care two days a week at $100 a day will be around $2000 better off a year.

* A family on $80,000 - both parent/s working, with two children aged under 6 in long day care three days a week at $100 a day will be over $3000 better off a year.

* A family on $150,000 - both parent/s working, with two children aged 6 and under in long day care three days a week at $100 a day will be more than $1000 better off a year.

Australian Associated Press