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Compressing your files

Last updated 1 June 2022

We recommend you compress ('zip') your files before sending them to us. Compression makes uploading faster, especially for large files, and allows you to send multiple files as a single compressed file.

How to compress files

You need to compress your files to a .zip file format.

Operating systems generally include file compression tools. For example, in Windows 7 and later, you would:

  • select your file or files in File Explorer
  • right click and select Send to then Compressed (zipped) folder.

You can use third-party compression tools, such as WinZip and 7-Zip.

Note: The current version of TrueZip is not supported. An error message 'Compression method 9 not supported' will display.

You can only compress a file or multiple files together. Don't include any folders in the compressed file and don't include compressed files within a compressed file.

Reducing upload times

The time to upload your file depends on the size of the file and your connection speed.

Most lodgments are less than 1MB and should take less than 2 minutes to upload on a broadband connection. Large files can take significantly longer.

Compressing your files can reduce the file size up to 10 times, greatly reducing the upload time. For example, a 100MB file may take up to 30 minutes to upload, even on a very fast connection. The same file may compress to just 10MB and send in less than 5 minutes.

Large files

You can use file transfer to test or lodge the full set of data you’re required to report. You don’t need to split the file.

We strongly recommend that you compress your file to reduce the upload time.

You don’t need to stay connected to our online services during validation.

Limitations on file compression sizes

Standard compression (Deflate) uses a 32-bit algorithm. This algorithm is mainly used by older versions of third-party file compression tools and the File Explorer in Windows XP.

The maximum file size is approximately 4GB. Note that Windows XP has a known issue where a zip file can become unreadable and corrupted if the file to be compressed is larger than 2GB. We recommend the latest versions of third-party compression tools such as WinZip or 7-Zip for files greater than 2GB.

Deflate64 compression uses a 64-bit algorithm. This algorithm is supported in the latest versions of third-party tools as well as Windows Vista, Windows Server 2008, Windows 7 and Windows 8. The maximum file size will easily accommodate any lodgment to us.

You cannot unzip files created from a file larger than 2GB using Windows 7 64-bit (right click and select Send to then Compressed (zipped) folder).