Before going on to find that a domestic UK provision that deemed an employee to be an independent contractor for purposes of computing his income did not have the effect of ousting his status as an employee for Treaty purposes, Lord Briggs stated (at para. 27):
There are useful but not conclusive dicta in reported authorities about the way in which, in general, statutory deeming provisions ought to be interpreted and applied. They are not conclusive because they may fairly be said to point in different directions, even if not actually contradictory. The relevant dicta are mainly collected in a summary by Lord Walker in DCC Holdings (UK) Ltd v Revenue and Customs Comrs [2011] 1 WLR 44, paras 37-39 …:
(1) The extent of the fiction created by a deeming provision is primarily a matter of construction of the statute in which it appears.
(2) For that purpose the court should ascertain, if it can, the purposes for which and the persons between whom the statutory fiction is to be resorted to, and then apply the deeming provision that far, but not where it would produce effects clearly outside those purposes.
(3) But those purposes may be difficult to ascertain, and Parliament may not find it easy to prescribe with precision the intended limits of the artificial assumption which the deeming provision requires to be made.
(4) A deeming provision should not be applied so far as to produce unjust, absurd or anomalous results, unless the court is compelled to do so by clear language.
(5) But the court should not shrink from applying the fiction created by the deeming provision to the consequences which would inevitably flow from the fiction being real. As Lord Asquith memorably put it in East End Dwellings Co Ltd v Finsbury Borough Council [1952] AC 109, at 133:
“The statute says that you must imagine a certain state of affairs; it does not say that having done so, you must cause or permit your imagination to boggle when it comes to the inevitable corollaries of that state of affairs.”