Adam Smith wrote that “the subjects of every state ought to contribute towards the supports of the Government, as nearly as possible, in proportion to their respective abilities, that is, in proportion to their revenue which they enjoy under the protection of the state” (Smith, 1776).. It is in favour of a progressive tax structure and implies that tax should be paid on a rate schedule. The UK uses this system on their income tax, with an allowance of £11,850 (as of 2018/19) (UK Government, 2017) tax free to help low receivers of income, and anything over is taxed at various rates based on the band in which they fall. The design of the rate schedule should reflect the best available evidence on how responsive people at different income levels are.

Certainty

This cannon suggests that the tax needed to be paid, the place and other procedural information should be certain to the tax payer. This protects the individual from exploitation from the tax authorities. This also means the government should be able to estimate the tax yield within a certain degree of accuracy, so expenses can be managed. The system should have some degree of flexibility so that changes are possible without damaging the economy or contentment of the people. It must cope with the changing needs of politics, with tax rates changing year on year to deal with contributing factors, but should clearly be announced, and change of leadership in short successions, with a minimum of 5 years in the UK.

Convenience

Every tax should be levied in such a manner and at such a time that it gives the tax payer maximum convenience. Tax in the UK is generally collected by either taking from the tax payer before they receive the rest of the money, known as the Pay As You Earn (PAYE) system, or they pay it directly to the government (HMRC).

Economy