If an enterprise is not registered for GST, then it will not charge GST on its supplies and consequently will not (or should not) issue a tax invoice.
If receiving an invoice from a supplier that is not registered for GST the table below applies:

ABN of Supplier quoted

YES Words “ Invoice” only should appear
Further clarification would be helpful with the words “Not Registered for GST”
NO 46.5% “Pay as you go withholding tax” (PAYGWT) will be deducted from payment
Statement by a Supplier (PDF 116KB)

It is possible to check the Australian Business Register [ABR] to verify that the ABN quoted is from an enterprise not registered for GST.

It is worth checking the ABR if you are in any doubt over whether GST should be being withheld.
Note: the ABR lists entities that have ABNs whether or not they have GST registration – those that have GST registration show an effective date.
Link : abr.gov.au

What if no ABN quoted?

The general rule is that if no ABN is quoted then tax at 46.5% must be withheld by the payer and handed over to the ATO.

However, you must not withhold tax if the supply is excluded from the ABN rule:

  • total payment less than $75 excluding GST
  • supplier is less than 18 years old and is not an employee and payments are less than $120 per week
  • supply is wholly input taxed
  • supply made in private capacity or as a hobby
  • payment exempt income for supplier
  • supplier non-resident
  • supplier not an enterprise

If you are unsure, ask the supplier to give you a written statement that the supply is excluded for one of these reasons – supplier declaration (see above).