The general rule is that damages for a breach of a contract for the sale of land are assessed at the date of the breach. The task is usually to compare the contract price with the value of the land a the time of the breach. If the value is greater than the contract price, the vendor has suffered no loss. But if the value is less than the contract price, it may be inferred that the discrepancy is an element of the vendor’s loss (Vitek v Estate Homes Pty Ltd  NSWSC 237 at ).
In Ng v Filmlock Pty Ltd  NSWCA 389 the NSW Court of Appeal heard an appeal by a purchaser of land from a judgment where the trial judge had assessed the vendor’s loss as being the difference between the contract price and the price obtained on a resale. The contract restricted the use of the resale price as an element in the quantification of loss to a resale within 12 months of termination but otherwise the vendor was entitled to damages for breach of contract. The resale took place more than 12 months after termination and therefore the general law applied. The land had declined significantly in value by the time of the resale.
The vendor argued that there was no available market as at the date of the breach of contract and therefore the resale price was relevant to the calculation of loss. The argument was based on a proposition said to be derived from the decision of the English Court of Appeal in Hooper v Oates  Ch 287: the correct date for assessment of damages for breach of contract is the date of breach only where there is an immediately available market for the subject matter of the sale.
Emmett JA, after noting that the English Court of Appeal did not explain what was meant by an “immediately available market”, said at :
“While a sale of land might take longer than the sale of other types of assets, it does not follow that there should be a departure from the general rule, which focuses on the value of the land as at the date of termination of the contract. There is good reason for that approach where the damages sought by the innocent seller are loss of bargain damages. The critical date is when the bargain was lost.”
While the appeal was successful the court accepted that in an appropriate case the interests of justice may require that “the date of breach” rule should not apply and damages may be assessed by reference to a later date, such as the contract price on resale. See: Johnson v Perez (1988) 166 CLR 351 at 367.
Gleeson JA said at :
“….whether a market value may be assessed in the case of land as at “the date of breach” is ultimately a question of fact. Of necessity, the sale of land will generally require a period to elapse for proper marketing. Unsuccessful attempts by a vendor to resell the property are not determinative as to whether there is no market for the land. Much will depend on the usual method of sale for the land in question having regard to its location, particular characteristics, the range of likely interested purchasers, and the time usually required for proper marketing of land of that type. Expert valuation evidence is likely to have a significant role.”
And at :
“It needs to be emphasised that that departure from the general rule is not a matter of discretion: Clark v Macourt  HCA 56 at  (Keane J). A vendor claiming damages assessed at a date later than “the date of breach” must demonstrate that there are particular reasons on the facts which would make it unjust to apply the prima face or “usual” measure of damages.”