First of all if you are contracting to a Plumbing Company, you would be earning more than $50,000-00 per year. You should of applied for an ABN. Secondly if 80% percent of your work is from the same Company, you will have to either fill fill the four criteria levels in the Ralph Report or go on wages.
The old PPS system is gone, so add 10% to the total of your invoices, if you don’t have an ABN, then the invoice will be paid les 48.5%