The going concern exemption is what keeps GST off the purchase price when you sell a business as a functioning operation rather than a collection of assets.
Technically, it is a Goods and Services Tax provision under Subdivision 38-J of the A New Tax System (Goods and Services Tax) Act 1999 (Cth) that exempts the supply of a going concern from GST, provided the seller supplies everything necessary for the enterprise to continue, carries it on until the day of sale, and both parties are GST-registered and agree in writing that the supply is of a going concern.
Every condition has to be met, not just most of them. Missing one, such as an asset the buyer needs to run the business that was accidentally left out of the sale, can turn an exempt sale into one that attracts GST, and that liability lands on the seller.
What you as a seller should ask your tax adviser: has every asset genuinely necessary to run the business been included in what is being sold, and is the written agreement about going concern treatment actually in the sale agreement itself, not just assumed.