From the WIA, original post here.

Date : 23 / 10 / 2015
Author : Jim Linton – VK3PC

As a part of the new SPECTRA system, the Australian Communications and Media Authority (ACMA) will send revalidation letters to all radio amateurs 90 days before licences are due to expire.  This letter, or email, has the ACMA licence number – however it does not include your callsign, or callsigns.  You can easily confirm callsigns associated with licence numbers online via the ACMA website. Link

A Validation Notice is sent to all licence holders, and not just radio amateurs.  The purpose of this is to allow licensees to check or change their details, or surrender a licence.  If the details are correct, and you do not surrender a licence, then the ACMA wants you to take no action, until you receive a Renewal Notice, which is the time to pay for the renewal.

The ACMA sends an invoice for renewing licence holders, and after you have paid a Renewal Summary will be sent out.  Is it worth also mentioning that the renewal notice will not contain your callsign so once again you may need to visit the ACMA website and lookup your licence number to confirm the callsign being renewed.  Link

Now here is an important reminder.  If the ACMA does not have your details correctly recorded, it cannot send these letters.  For instance, you may have changed your postal address, or failed to update them with your current email address.

Renewal is always the licensee’s responsibility.  Please check now to avoid delays, or cancellation of your licence, and your callsign being re-assigned to someone else.  The ACMA contact details are: Telephone 1300 850 115 and email info@acma.gov.au