3 yrs ago I was introduced to MLM business the women who introduced me to it told me to get an ABN number I did but then I didn't do anything with the MLM business, and I didn't do anything with the ABN. Can I just cancel it or should I do tax return?

Asha. Good afternoon. I am not a Tax Accountant, so am unable to give specific Tax Advice, however you can cancel an ABN at any time it is no longer required. If you registered in the capacity of a Sole Trader, then your personal Tax Returns, should have captured all the business activity (in your case - None). You should also look into whether you registered for GST, although if you have not been requested by the ATO to do the Business Activity Statements, it is likely that you are not GST registered. Google the term "ABN Search" you will find a free website that will inform you of your ABN / GST status.
If you are looking to borrow money and your ABN remains registered, many lenders will ask for evidence from your Accountant that the ABN is not trading and has no outstanding liabilities. Could considerably slow down a loan application. If you never intend to use it in the future, probably best to close it off. You can re-active again in the future if the need arises.
Hope this helps
Ken Olds
Customers First Mortgages & Insurance
1300 ASK KEN

Hi Asha,
If there was no business activity whatsoever over the past 3 years then you should be fine to simply cancel the ABN. Keep in mind there may be other reasons you need to lodge a Tax Return (e.g. Receive wages or other income during the year).

Hope this helps, have a good week.

Ben Andrews