Australians are being reassured they won't be fined for handing in late census forms.

The federal government has moved to quell fears people will be fined $180 a day if they don't fill out their form on August 9.

It comes as the Australian Bureau of Statistics' move to an online form causes confusion for people who want to fill out the old paper version.

The ABS has had to put hundreds more staff and phone lines in place to cope with unexpected demand after its 24-hour phone line for those requesting a paper form was jammed, having been inundated with more than 500,000 calls.

That sparked a wave of panic with people fearing they wouldn't receive their paper forms in time.

Treasurer Scott Morrison insisted penalty notices were a last resort for the ABS and were only issued where there was a clear unwillingness to participate.

The ABS is reassuring households they will receive all the necessary forms before census night on August 9.

They won't be fined if they don't complete the form in time.

"We will be giving people ample opportunity to complete their census in the weeks following census night," head of the census program Duncan Young said.

Census officers would visit homes that hadn't completed their forms from mid-August to remind and assist them, he said.

About 65 per cent of people are expected to complete the census online, saving taxpayers $100 million.

Small Business Minister Michael McCormack hopes the extra call centre staff will ease phone line congestion and expects requests for paper forms to taper off in coming days.

"People who can't get through to the call line are urged to keep persevering," he told ABC radio.