An individual's tax rate depends upon many things. First, in the US, there is a income tax imposed by the federal government. The tax rates under the federal income tax range from 15% to 39.6%. However that is not the full story. The federal government also allows various deductions and exemptions which are "phased out" as income arises. This means that the amount of the deduction allowed goes down as one's income rises. The effect is that the actual tax rate on an additional dollar of income is more than the stated rate. For example, assume an individual earns $100,000 and has a deduction for $20,000 for mortgage interest. Further assume that, if the individual were to earn one more dollar of income, the deduction for mortgage interest would be phased out by 50 cents. In that case, the individual's tax on the $100,000 of income with the $20,000 deduction, assuming a 30% rate, would be $24,000. In contrast, the individual's tax on the income $100,001, with a deduction for only $19,999.50, would be $24,000.45. The result is that the additional one dollar of income resulted in additional tax of 45 cents, an effective tax rate of 45%, even though the stated rate was 30%. This example is greatly simplified but illustrates that a reduction in a deduction or exemption has the same effect as increasing the stated rate of tax.

A further complication is the taxes imposed by other governments. In many countries, provinces or states or cities impose tax. In some jurisdictions, such as Canada, the provincial income tax is imposed on top of the federal income tax and is calculated on the same or a similar base to the federal income tax but does not affect the federal tax payable. In that case, the provincial rate may simply be added to the federal rate to determine the total rate of tax. In other jurisdictions, such as the US, state income tax is deductible for federal income tax purposes. This means that, for example, a California resident subject to California tax at 9.3% does not effectively pay 9.3% of California tax. That California tax would result in a tax saving on the federal return that would offset about 1/3 of that California tax. Again, some states or provinces may phase out certain deductions as income creases, resulting again in an effective rate that is higher than the stated rate.

Finally, many jurisdictions impose taxes that are based upon income but are not technically income taxes. The best example of this is payroll taxes such as social security tax/self employment tax in the US or CPP/EI in Canada. These taxes are imposed as a percentage of income up to a certain level and are collected through the employer, similar to income taxes. These taxes are often flat taxes because the rate is the same on each dollar of income up to the threshold. The effective rate of these taxes can be very high, especially for self-employed individuals who normally pay twice the rate of employed individuals. In some cases, these taxes are deductible for income tax purposes.

The short answer to "what is my tax rate" is that it depends on many things. It also means that taxpayers should not blindly accept a politician's statement that he or she wants to lower tax rates. It is quite possible to lower stated tax rates without having any real effect on tax payable.