It's a scam. I have recirced the notice for at least 4 times. They use the title as 'the Dun&Bradstreet Ptd Ltd'. Don't get fooled by it. The real company's free call number doesn't match with the one it shows on this notice. They also use quite aggressive words such as' issue of garnishee notice' which ATO would not do. Be aware that the ATO will not contact anyone in personal letter. Anyway, ignore this scam or report it to the ATO online.

Had a letter claiming to be from Dun & Bradstreet, as authorised collection agents for ATO, quote "Dun & Bradstreet have recently taken over the responsibility of collecting your overdue Income Tax debt on behalf of the Australian Tax Office. This is due to continued non action to prior correspondence with another collection agency. All prior correspondence relating to this debt should be disregarded."
It goes on to to say the balance of $1770 is due immediately. Interestingly the last income tax assessment resulted in a refund, so it is obvious this is a scam.
In addition the space on the payment slip that should show the ATO Code is blank and on the reverse side showing methods of payment, the correct biller code 75556 for the ATO is shown with no reference number.

got an SMS asking me to call this number immediately. claim to be Dunn & Bradstreet but number does not match their number. am not going to reply as is possibly a scam. if they want me for something important, they can phone me or write...