Beware the time bar in future payment agreements : tax advice

What happens if an agreement for the sale of property is taxed in one year, but the sale is later cancelled and the property is returned, with loss of some of the assessed gain? Is capital gains tax (CGT) paid in the year when the deal was done, or is it recalculated? This was more or less the thrust of the questions posed before the Western Cape High Court in the matter of New Adventure Shelf 122 (Pty) Ltd v The Commissioner SARS (case number 7007/2015). A certain valuable property was sold in an agreement that provided for ownership to pass in the 2007 tax year. However, the purchaser, who intended developing the property, was to make payments over the term of the contract. The CGT was paid in 2007 and was, quite correctly, a considerable sum.