Selling a car without RWC what are my obligations?

[Cuppa]

I would even go one step further and put the transaction time on the paper receipt as well.

Plus 2 copies, both signed by both parties, one copy each.

Is it the same in Victoria?

Good question, I *think* that if the car is purchased legally with rego by someone from another state, they have purchased the balance of the rego, & can claim it back from VicRoads when they re-register it in their state, but I'm not 100% certain on that.
I've only sold interstate twice & both times I sold without rego. One was a motorcycle with expired rego I freighted to the buyer (Nisshead), & the other the bus which I drove to NSW, removed the plates on arrival & got the balance refunded from VicRoads.