How much more expensive is it to maintain a company registration when compared to a soletrader?
Generally speaking, other than the one-off start-up costs of registration (approx $500 – $1,000), not much more.
Annual ASIC cost is around $245, tax compliance and financial account preparation won’t cost you much more than what you are already paying for a business tax return as a sole trader, the only thing that changes in that regard (which may increase the cost marginally) is the actual tax return which is prepared.