Should the poor be afraid of a “Flat-rate” tax?

I believe it depends on three things:

  1. How income is defined;
  2. The tax-free personal allowance; and
  3. The tax rate

Realised comprehensive income

In the UK there are three taxes that could be consolidated into a single income tax. These three taxes are Inheritance Tax, Capital Gains Tax, and the current income tax. All three levy tax on assets that flow from one party to another. Each of the three taxes has a separate and different  tax free allowance associated with it and are taxed at different rates.

A realised comprehensive income tax would make no distinction between these asset flows – all flows would be taxed as income. The annual inflows of assets received by an individual from the three sources would be aggregated and taxed as realised comprehensive income after deducting the individual’s annual tax-free personal allowance.

The advantages of a realised comprehensive income tax are:

  1. Simplification. Inheritance tax and capital gains tax would be brought under a single regime;
  2. Less incentive would exist to engage in tax avoidance;
  3. Legacies would be taxed according to the recipient’s circumstances, not the donor’s. This is more just as the recipient’s entitlement to the assets has not been derived through labour or through an identified contribution to society. Many donor’s feel resentment when it is their circumstances that determine the tax due on bequests, as is the case currently.

The annual tax-free personal allowance

Rolling up all three types of income into one obviates the need to have separate tax-free personal allowances for each of the three sources. Setting a single annual tax-free personal allowance of, say, £50,000 would provide generous relief to those whose comprehensive incomes are low or in the middle. It also supports simplification of the tax system.

The tax rate

In the presence of an annual tax-free personal allowance a flat-rate tax would by definition be a marginal rate (not an average rate).

Many ‘small-staters’ and their ilk hold that the state’s share of someone’s income should never exceed 50%. Setting the marginal rate of income tax to 50% respects this limit because of the annual tax-free personal allowance. In fact, many individuals with taxable income will have average tax rates that are far below the marginal tax rate of 50%.


Suppose the annual tax-free personal allowance has been set to £50,000 and the single rate of tax is 50%. An individual with a realised comprehensive income (earned + unearned + capital gains + bequests) of £100,000 would be liable for tax of

 0.5 x (£100,000 – £50,000) = £25,000

which is 25% of realised comprehensive income received in the year.

Here is a graph which shows average tax rates against realised comprehensive income in a flat-rate tax system with the parameters described above.


The average tax rate will get ever closer to the 50% marginal rate as comprehensive income gets larger and larger.

Conclusions and Summary

What I have shown is that flat-rate taxes, so often proposed by ‘small-staters’ et al, should not axiomatically be feared. This is because the fairness of such schemes can depend on their parameters and the definition of income. Flat-rate taxes need not mean low-taxes, as hoped for by their proponents. The battleground is really about the parameters of such a scheme, not about whether a flat-rate tax system is desirable in itself. A judicious selection of parameters can ensure equity, whilst simultaneously meeting the objections of ‘small staters’ to wealth taxes and high average tax rates on conventional income.

I suggest, in the wake of Piketty, that taxing flows of assets as income is a more feasible way of addressing runaway inequality than imposing taxes on stocks of assets (wealth taxes). The exception to this rule would be a land value tax, which can be perceived as a rental charge on privately sequestered natural assets. It is difficult to sustain a moral objection to taxing  a stock in the case of land.

I have not attempted to cost out this flat-rate tax proposal, either with the proposed or alternative parameters. It may be that a flat-rate tax system would raise less than the current sum of capital gains tax, inheritance tax and conventional income tax. If so, then perhaps a Land Value Tax would be needed to plug the gap. The challenge, as I see it, is to find ways of financing generous public services whilst simultaneously defeating the (sometimes spurious) moral objections that Libertarians et al advance.


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