Can I tow a trailer with an ATM higher than my car’s braked tow capacity?

Yes you can.

Here is an example – your trailer has an ATM, max weight, of 3000kg. It actually weighs 1000kg unladen. You place on the trailer a load of 500kg, making the total to be towed 1500kg.

You can tow that with a car rated for 1500kg or more. The fact the ATM say 3000kg is irrelevant.

Proof?

Well, this example is not written specifically into any regulations far as I know, BUT equally, there is also no regulation stating that you must have a towcar capable of towing the trailer at ATM. Here for example is Vicroads’ advice on towing:

To me that’s the towed weight, not maximum, and it refers to the maximum weight recommended by the caravan manufacturer as a seperate point.

Whilst I’m at it, 750kg trailers *may* need brakes if the unbraked towing capacity is of the towcar is less than 750kg. So you cannot always tow 750kg trailers without brakes.

What I can offer is this direct question to Queensland TMR. I have not asked all the other states, but my experience is that on matters like this they agree, and again, nobody has ever provided any documentation otherwise, only “so and so said”.