SDLTM05010 - Scope: How much is chargeable: Contingent, uncertain or unascertained consideration: General FA03/S51
Where a contingency affects the eventual amount of consideration, purchasers must calculate the consideration on the basis that the contingent amount will be payable.
Where the consideration is uncertain or has not yet been ascertained, for example, where it is based on profits in accounts which have not yet been drawn up, purchasers must make a reasonable estimate of the final consideration as at the effective date of the transaction.
See the example at SDLTM05010a.
In certain circumstances an application can be made to defer payment of stamp duty land tax under FA03/S90. See SDLTM50900.