For GST-registered tradies in Australia, invoices need to say "Tax Invoice" and show GST as its own line, not folded into the total. Get this wrong and it can cause problems at tax time, or hold up payment while the client's bookkeeper queries it before approving anything. 

A free invoice generator australia tradies can use without signing up makes this easier to get right from the start, since the tax field is built in rather than something you're calculating manually on every job you complete. 

As a trade business grows past one or two people, proper invoicing software, with saved client details and recurring invoices for regular contracts, tends to pay for itself in time saved. But for anyone just getting their invoicing sorted, starting free and upgrading later is a perfectly reasonable approach.