Should you sell your farm and the transaction is subject to VAT, ensure that the Agreement of Sale specifies clearly whether the agreed purchase price includes or excludes VAT.
If VAT isn't specified, the purchase price is deemed to be inclusive of VAT. If that isn't what you intended, in other words, if you anticipated the purchaser paying the VAT over and above the full purchase price, you are in for a disappointment, and a substantial loss - you will be liable for VAT at the "tax fraction" (which comes to 12.28% of the gross price).
You can try to override the deeming provision by proving that the actual intention - of both you and the buyer - was for the price to be VAT exclusive. That's never going to be easy and could result in time consuming and expensive litigation.
The Supreme Court of Appeal confirmed the above principle in a recent case, Van Aardt v Galway (923/10) [2011] ZASCA 201.