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Why is My Property Data Wrong?

Author: Kylie Davis
Source: CoreLogic

Property data is ubiquitous these days. It appears in apps, in reports, it’s available online. You can get an understanding of what your home is worth by asking your mortgage broker, your real estate agent, or just typing your address into Google.

But sometimes the valuation you see – or the property details – don’t appear to be right. Or the photos are completely out of date. In the case of units, information about your individual apartment can sometimes be missing altogether. If big data is so clever, how can that be? And if the property details seem inaccurate about your home, does that mean you should discount everything you see?

To understand why the data about your individual property is not as you expected, it helps to understand how property data is collected and how your home therefore, may have slid under the radar. Big data after all, is made up of billions of small individual data points. It is also really helpful to understand that your property data can be easily corrected and updated.

Here’s what you need to know:

Property data collection companies have data collection methods that are biased towards sales information. This means that every time a property lists for sale on the market, that information is captured by the data company after it is shared by either the listings portal or real estate agency. In some cases, it is even keyed in from newspaper advertisements.

Sales information is rich. It includes up to date photographs, details about features – how many bedrooms, bathrooms and car parking spaces and often includes additional insights such as when it was last renovated, quality of the fittings etc.

This information is overlaid against ‘baseline’ information that the company has collected about all properties within an area. Usually this information comes from government sources such as the Land Titles Office, or Valuer General’s Office. But this information is usually basic and includes limited information such as the address, last sale date, last sale amount and owners name/s. At CoreLogic – Australia’s largest provider of property data – we then enhance that information by augmenting with other datasets and elements such as aerial imagery and internal imagery.

So the property data that is the most accurate within a property database is always going to be a property that has sold. If you’re having trouble finding information about your property it is most probably this reason – because your property has not been sold for a long time (before the mid-1990s) or because you have significantly renovated or rebuilt it since you purchased and our system doesn’t ‘know’ that it’s been updated. Battleaxe blocks can also pose an issue as they can’t be seen by Google street images.

Units are a particular challenge if they are in very old blocks or if they are being sold off the plan. You may be able to see the address in the database, but not the individual unit.

What can you do if you have no intention of selling your home in the near term, but would still like to understand its value based on its current features?

Well, updating your data is easy. If your house or unit does not appear with the online valuation or report as you believe it should, send an email to

You should advise us of:

  • The address
  • Type of property
  • Your name and contact details
  • Advise us of any updated features in as much detail as you wish
  • Attach any photos if these are available.

Changes are usually made within 24 hours and we will send a confirmation to let you know when they have been done so you can rerun your report or online price estimate and get refreshed information.

Will it make a difference? Very likely. If the changes you have made to your home are significant – such as a knock down and rebuild or major renovations – updating the data can put you in a completely different price bracket. This is because the algorithms running at the back end of the data will evaluate your home against other properties that are a more suitable match. If your change is just the addition of a single room, a deck, or a kitchen refresh, the automated valuation may not change significantly.

Remember that automated valuations and price estimates are just that – estimates which are created by algorithms based on similar recent sales. If you still feel the estimate is not quite right, contact a real estate agent to get a more professional view into what it is likely to sell for.

Property data from CoreLogic powers websites such as, and and is also now included in Residex. It is also used in reports supplied by many major banks and mortgage brokers.  

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Kylie Davis
Head of Marketing, Property Services and Content

Kylie Davis is the Head of Property Services and Content Marketing at CoreLogic.

Published: 22 February, 2017.