Auskey is being retired at the end of March 2020 and is being replaced by mygovID. You must have a mygovID for any of your business dealings with the ATO.
mygovID should not be confused with a mygov account. You will need a mygovID if you have a business to access your business data with the ATO.
If you have a trust with a corporate trustee the instructions have an extra step which is highlighted in Step 3 below.