Prime Minister Malcolm Turnbull has accepted an apology from his Employment Minister Michaelia Cash after she failed to disclose an investment property on time.

The West Australian senator agreed to purchase a $1.4 million investment property in Perth in November and settlement occurred on December 9.

But the property was not added to Senator Cash's register of interests until January 21 and an extra mortgage to finance the purchase was not listed until February.

Politicians must update their register of interests within 35 days and may be accused of being in contempt of Parliament should they knowingly fail to disclose purchases.

Mr Turnbull said Senator Cash missed the reporting deadline by eight days and she was "mortified" by her mistake, which has been described by her office as an "inadvertent oversight".

The Prime Minister said he was disappointed by the oversight and he had accepted her apology.

"The public hold us to very high standards and we have to comply with them," he told Melbourne radio station 3AW.

"She is a very hard working and punctilious Minister and she's had an oversight here and she's very sorry about it."

A spokesman for Senator Cash said her register of interest was corrected two weeks ago.

Federal Government frontbencher Josh Frydenberg said Senator Cash's indiscretion was a "very minor" issue and there were bigger issues to tackle.

"We're all conscious of our obligations and I think in scheme of things this is very minor," he said.

"It's been corrected, there's nothing to hide here and we just need to get on with the job of governing for all Australians."

The West Australian is not the first politician to fall foul of reporting requirements.

Labor frontbencher David Feeney failed to declare a $2.3 million house on his parliamentary register of interests, with his office also claiming it was an oversight.

In 2010, the then opposition leader Tony Abbott was criticised for changing his mortgage provider and not updating his pecuniary interest register for two years.