A Canberra woman who defrauded Centrelink of more than $35,000 has been ordered to repay the money and spend weekends behind bars for the next five months.

It was the second time Jook Deng Dau had been convicted of swindling Centrelink. A NSW court in 2009 imposed a two-year good behaviour order after Dau was caught receiving $9000 in fraudulent carers payments.

The court heard on Monday that Dau claimed unemployment benefits and failed to declare her income during two periods between 2008 and 2011.

The 28-year-old pleaded guilty to receiving a financial advantage knowing she was not eligible for it.

She also pleaded guilty to a Commonwealth charge of obtaining financial advantage.

The first charge related to a period between March 2008 and May 2009 when Dau received about $14,000 in benefits.

The second offence took place between August 2009 and February 2011 and involved about $20,000 in payments.

The court heard Dau claimed the $20,000 while she was facing charges in the NSW court and continued to collect welfare uninterrupted after.

Magistrate Peter Morrison said Dau on 73 occasions, as part of reporting requirements, falsely stated that she had not earned an income. But he said she had, in fact, made about $50,000 between March 2008 and May 2009 and $55,000 from August 2009 to February 2011.

Mr Morrison sentenced her to five months periodic detention, to begin on Friday.

Mr Morrison said he had taken into account Dau was the sole carer of her 11-month-old son. But he said the penalty must take priority over other considerations.

The magistrate said the seriousness of the offence meant a jail term was necessary.

"The abuse of the social security system jeopardises the system itself," Mr Morrison said.

He also ordered the single mother to repay the $35,389.99.