You can claim the tax free threshold for withholding purposes on 1 job in Australia. The others you need to withhold tax on any money earnt.

However, in my opinion technology being what it is now, I don’t see a reason the tax office couldn’t just direct businesses to withhold a certain amount based on overall earnings. May be a touch more complicated, but most businesses sending this information to the ATO throughout the year anyway…

There definitely are ways around this problem.

But not with paper forms, and it seems the US are in the dark ages when it comes to tax administration.