Tracey Donaldson* says her problems began when a bill arrived in the mail last month.

Key points: The bill was meant for someone with the same name and same birth day and month

The bill was meant for someone with the same name and same birth day and month Ms Donaldson was warned she could be prevented from travelling overseas

Ms Donaldson was warned she could be prevented from travelling overseas Centrelink apologised for the error and said it was an isolated incident

It was a Centrelink debt for $45,500.

The letter was intended for another woman with the same name, who lived in a suburb with the same name, in a different state, said Ms Donaldson, whose name has been changed for legal reasons.

The woman was also born on the same day of the same month as Ms Donaldson, but in a different year.

"I would be mortified if I owed that amount of money and someone else got my letter," Ms Donaldson said.

The 43-year-old Sydney woman called Centrelink to explain it had the wrong person, but her customer number did not match that of the woman who had acquired the debt.

She was told she would not be able to contest the bill as she could not prove her identity.

The debt notice, which arrived 10 days before Ms Donaldson's overseas holiday, also contained a travel warning.

Part of the Centrelink letter sent to Tracey Donaldson.

The warning threatened Ms Donaldson with a Departure Prohibition Order, which would stop her from travelling overseas.

"I don't have panic attacks very often, but I actually started hyperventilating," she said.

"I was so frustrated and no-one was giving me information.

Ms Donaldson approached her local federal MP, Julie Owens.

The Labor MP's office contacted Centrelink on her behalf and confirmed the letter was intended for someone else.

Ms Donaldson said the debt was an alleged overpayment of a parenting allowance, but she did not have children or receive welfare.

"It was bad for me, but I feel like the other woman's privacy was breached too," she said.

She later received a call from the welfare agency conceding there had been a mix-up.

"He said there was no hold on my passport and my debt was now cleared."

Department of Human Services general manager Hank Jongen apologised for the error.

The bill was over a parenting payment, but Ms Donaldson doesn't have children. ( ABC News )

"We can assure the community this is an isolated incident and there are no wider issues," he said.

It is not the first time Centrelink has been accused of mistaken identity or breaching customer privacy.

Last year the Office of the Australian Information Commissioner (OAIC) referred another case of mistaken identity to the Department of Human Services.

And in 2018 a Melbourne woman claimed Centrelink accidentally gave her another client's private information, including bank details.

Terry Carney from the University of Sydney said he was aware of similar cases.

"I know a senior professional whose child was stopped while returning to Australia after a faulty debt notice was sent out," he said.

Professor Carney said the Sydney man ended up paying his child's debt to avoid the time it would take to contest it.

Bill Shorten, the Shadow Minister for Government Services, accused the Federal Government of using a "disturbingly low" standard of proof when issuing debt notices.

"Now they are going around hitting innocent Australians for $45,000 simply because they have the same name as someone else? That's not good enough," he said.

Australian Council of Social Service chief executive Cassandra Goldie said Ms Donaldson should have received a phone call before the bill arrived.

"Centrelink's guidelines advise staff to call individuals before issuing large debt notices to ensure it's being sent to the right person," she said.

Bond University professor of data science Steve Stern said mix-ups were probably very common.

"I imagine this probably happens hundreds of times but gets cleared up when a human staff member double checks the computer data," Professor Stern said.

He said no single government agency held all personal details, so data did not always link up correctly when shared between them.

*Tracey's surname has been changed for legal reasons.