Physician Finances

Marginal Income Tax Brackets Versus Effective Income Tax

Forget about everything that you think you know about income tax brackets… they are one of the most misunderstood parts of the American tax system. How many times have you heard someone say “More income might push me into a higher tax bracket”? Yes, it will but no, you shouldn’t care in the least. The reason is that Federal income tax brackets are marginal tax brackets. Because of this no American pays income taxes at the tax rate of the bracket that they are in. Instead, we pay the effective tax rate which is always lower than the marginal tax bracket. The following table shows the current Federal income tax brackets.

Many people mistakenly think that their income tax rate is the same as whatever the tax bracket that their taxable income falls into. But that is not exactly correct. The marginal tax system results in everyone paying the same tax rate (10%) on the first $19,751 that they make. Then everyone pays the same tax rate (12%) on the next $60,500 that they make and so on up each tax bracket. The graph below illustrates how this works:

The result is that for any given taxable income a person earns, their federal income is a blend of the individual tax rates for each of the brackets that comprise their total income. In addition, each taxpayer can take the standard deduction from their gross income: $12,400 if filing single and $24,800 if married and filing jointly. The standard deduction results in everyone’s taxable income being lower than their total gross income. As a result, even people in the lowest income tax bracket pay a smaller effective tax rate than the marginal tax rate of that bracket. The next graph shows the current marginal tax brackets for Federal income tax in the dotted line and the effective tax rate in the solid line.

From this graph, you can see that the effective tax rate (what you actually pay) is always less than the tax bracket that you are in. It also shows that the effective tax rate does not jump up when your income increases enough to put you into a higher marginal tax bracket. Instead, the effective tax rate goes steadily up at a relatively constant rate for every dollar more you earn. Periodically, congress will set new tax brackets. The graphs below compare the 2016 and 2020 brackets.

As you can see, trying to figure out what those tax bracket changes mean for any one person at any given income is difficult. So, let’s look at how the 2020 brackets affect people at different incomes:

The above graph shows the tax brackets at the end of the Obama administration (blue) versus the tax brackets at the end of the Trump administration. Just looking at a tax bracket table can be hard to interpret – what is important is your effective tax rate and not the marginal tax bracket. The table below shows the effective tax rates during the two administrations:

The effective tax rate that taxpayers of every income dropped during the Trump administration. The reduction in effective tax rates was fairly consistent across all incomes, ranging from a drop of 3.7 to 5.9 percentage points. Some people focus on the top tax bracket (currently $622,051 and 37%). But as was demonstrated earlier in this post, no one pays an effective tax rate as high as their marginal tax bracket. So even a person with an extremely high gross income of $700,000 per year only pays an effective tax rate of 26.7%.

Tax rates go up and down with different administrations. Tax cuts are an enormous crowd-pleaser for voters. However, eventually, deficits catch up with tax cuts – the government cannot spend money on services that voters demand and then tax raises ensue. In general, taxes go up when Democratic presidents are in office and go down when Republican presidents are in office. The graph below shows the marginal tax rate for the highest tax bracket over the past 36 years:

So, don’t fear being in a higher income tax bracket. Indeed, you should try to be in as high of an income tax bracket as you can. But it does make retirement planning complicated. Let’s say you have an option of putting retirement savings in a regular 401(k) or a Roth 401(k) this year. If you put money in the regular 401(k), the money will be invested pre-tax and then you will pay regular income tax on the withdrawals when you take the money out in retirement. If you instead put money in a Roth 401(k), then you will pay income tax on the money now and then you will pay no tax on the withdrawals when you are retired.  The strategy is to pay income taxes when you have the lowest effective tax rate. The problem is that you cannot predict today what the effective tax rates are going to be when you retire.

As an example, assume you are making a taxable income of $150,000/year today. Your effective tax rate in 2021 is 14.1%. Now assume you will have a taxable income of $100,000/year when you retire. If tax rates are the same in your retirement year as they are now, then your effective tax rate will be 11.7% in retirement and so you would be better off putting your money in a regular 401(k) today to minimize your overall tax burden since your retirement income tax rate will be lower than your current income tax rate. However, if whoever is president when you retire goes back to the same tax rates we had in 2016, then that taxable income of $100,000/year in retirement will result in an effective tax rate of 15.6%. This would be higher than your current tax rate on your taxable income of $150,000 today of 14.1%. So, in that situation, you’d be better off putting your retirement investment in the Roth 401(k) since your tax rate will be higher in your retirement year.

No one has a crystal ball to predict the tax rates of the future. More than likely, they will go up some years and go down other years. So, should you put your retirement investment in a regular 401(k) or a Roth 401(k)? The best option is to do both and split your investment with half in a regular 401(k) and half in a Roth 401(k). When you are retired, if the effective tax rates go up one year, then take money out of your Roth 401(k) that year. On the other hand, if the effective tax rates go down the next year of your retirement, then take money out of the regular 401(k) that year. Your best defense against variable tax rates in your retirement years is a diversified portfolio that includes both the regular 401(k) and the Roth 401(k). If you work for a non-profit company, then the same goes for a regular 403(b) and a Roth 403(b). If your company does not offer the Roth 401(k)/403(b), then put some money in the regular 401(k)/403(b) and some money in a Roth IRA (depending on your income level, you may need to initially put money in a traditional IRA and then do a Roth IRA conversion to avoid penalties).

In a letter to Jean-Baptiste Le Roy, Benjamin Franklin famously wrote: “Our new Constitution is now established, and has an appearance that promises permanency; but in this world nothing can be said to be certain, except death and taxes.” I would add to that that the only thing certain about taxes is that the rates will be different in the future.

March 15, 2021

By James Allen, MD

I am a Professor Emeritus of Internal Medicine at the Ohio State University and former Medical Director of Ohio State University East Hospital