I've come across an excellent post on the Bizify website which explains commonly used business registration acronyms.
Head across to Bizify's 'What is ABN, ACN AUSkey? - World of business registration acronyms' by Ritesh Anan.
The article was posted a couple of years ago. It includes these acronyms and is relevant today:
ABN Australian Business Number
ACN Australian Company Number
ASIC Australian Securities and Investment Commission
ATO Australian Taxation Office
AUSkey Single key access to government online services like ASIC Connect,
business name search etc.
GST Goods and Service Tax
PAYG Pay As You Go
PAYGI Pay As You Go Installment
PAYGW Pay As You Go Withholding.
TFN Tax Filing Number