More than half a million Australians are missing out on Medicare rebates worth about $110 million because they have not provided their bank account details, according to the Federal Government.

Key points: Privacy laws prevent Medicare from contacting ATO to retrieve information

Privacy laws prevent Medicare from contacting ATO to retrieve information Government believes people have forgotten to update their details

Government believes people have forgotten to update their details Around 670,000 people could be owed money

Medicare has been writing to 670,000 customers who have missed out rebates for doctors' visits and other services.

But Human Services Minister Michael Keenan said many were still off the books.

"I couldn't see why anyone wouldn't put their bank account details in the system to get what they're owed," Mr Keenan said.

"We have written to people asking them to do that, reminding them about this.

"People live busy lives, there's a lot going on, these sorts of things can slip through the cracks."

Mr Keenan believed people had just forgotten to update their details, rather than having complained about handing over the information.

"It was several years ago that we stopped issuing cheques, no one really issues cheques any more," he said.

"It's far simpler, of course, for people just to go to their doctor and get the rebate paid directly to them.

"We do it across the whole government now. For example, the Australian Taxation Office has been doing that for a long period of time."

Mr Keenan said people could nominate whether they would receive the funds or someone else, for example teenagers with their own Medicare cards could nominate their parents bank account to receive any funds given it was likely they were the ones paying the medical bills.

The Minister's office said Medicare could not simply contact the ATO to request the account details of people it was chasing because of current privacy laws.