That Qld advice sounds right for the ACT, so that’s more than half way to Vic.
Whatever the situation, as far as the OC is concerned the debt goes with the unit/lot so the buyer is stuck with any debt associated with the unit if it has not been deducted from the purchase price and paid during the conveyancing.
We learned that when the lawyer doing our conveyancing had their trust account frozen by the local law society on the day of our settlement. I have no idea what our lawyer had done or was suspected of having done but the cheques for several thousand dollars that were deducted from the purchase price to pay the previous owner’s outstanding levies and rates were also frozen and we had to write pleading letters to the OC and local government to be given additional time. Eventually the accounts were unfrozen and we didn’t have to pay but it was a worry for a while when we had no spare cash at all.
Back to the question: If there is a contract in place and then a levy arrives with a due date before the settlement date, then I would guess the seller would pay and its just the seller’s bad luck that this arrived before responsibility passed to the buyer. The seller could just stick with the contract and ignore the levy, but then the buyer’s conveyancer could, I think, deduct the overdue debt from the purchase price in order to pay the money owing to the OC on the unit. I guess the seller could decide to pull out of the sale but they would still be stuck with paying the levy. All that is only guessing though. I have only ever bought one unit, the one I am in.