If you have 4 or less employees, you can report to the ATO using a payroll solution that supports Single Touch Payroll from 1 July 2019. 
I want to start reporting from 1 July 2019.

If you are a micro employer, there is a range of no-cost and low-cost Single Touch Payroll (STP) solutions available now in addition to existing commercial STP solutions. Find a product suitable for your needs by checking the STP No-cost and low-cost register now!

The no-cost or low-cost solutions have been developed for micro employers (those with one to four employees) who need to report through STP but do not currently have STP ready software. These solutions may include mobile apps, simple reporting solutions and portals.