While Northern Territory does not issues specific painting licence, it does recommend obtaining an Australian Business Number.
In order to be recognised as trade professionals by organisations such as Master Painters Australia, it is recommended that painters obtain a CPC30611 Certificate III in Painting and Decorating or RPL assessed equivalent qualification.
The Australian building and construction industry is highly regulated, which results in the highest quality of international standards. The above processes outline how you can obtain your builder's licence by state.
It's good to remember that other options do exist. Experienced individuals need not be required to spend any unnecessary time in the classroom.