20. Machinery provisions.

It is important to distinguish between charging provisions, which impose the charge to tax, and machinery provisions, which provide the machinery for the quantification of the charge and the levying and collection of the tax in respect of the charge so imposed. Machinery provisions do not impose a charge or extend or restrict a charge elsewhere clearly imposed1. Once a charge is imposed, the taxpayer may waive the machinery of assessment; for example he may pay tax under an agreement to do so without insisting upon the formality of an assessment