Tax brackets determine how your income is taxed at various rates. The House and Senate versions of the Tax Cuts and Jobs Act each proposed different sets of income tax brackets, both of which vary significantly from the current setup. Here's how those different tax bracket options could play out if one of the two bills becomes law. 2018 tax brackets under the current tax code Despite the uncertainties about tax reform, the IRS released its numbers for the 2018 tax brackets as they stand under the current tax code. If tax reform doesn't happen in time for 2018, you'll use whichever of the below tax brackets applies for your filing status for the year: Bracket Single Filers Head of Household Joint Filers 10% $0 to $9,525 $0 to $13,600 $0 to $19,050 15% $9,526 to $38,700 $13,601 to $51,850 $19,051 to $77,400 25% $38,701 to $93,700 $51,851 to $133,850 $77,401 to $156,150 28% $93,701 to $195,450 $133,851 to $216,700 $156,151 to $237,950 33% $195,451 to $424,950 $216,701 to $424,950 $237,951 to $424,950 35% $424,951 to $426,700 $424,951 to $453,350 $424,951 to $480,050 39.6% above $426,700 above $453,350 above $480,050 2018 tax brackets under the House Tax Act The House version of the Tax Act, which passed in the House of Representatives on Nov. 16, consolidates the current system of seven tax brackets into a mere four brackets. Here's how your income taxes will play out if this version of the Tax Act becomes law: Bracket Single Filers Head of Household Joint Filers 12% $0 to $45,000 $0 to $67,500 $0 to $90,000 25% $45,001 to $200,000 $67,501 to $230,000 $90,001 to $260,000 35% $200,001 to $500,000 $230,001 to $500,000 $260,001 to $1,000,000 39.6% above $500,000 above $500,000 above $1,000,000 2018 tax brackets under the Senate Tax Act Here's how the Senate Tax Act's bracket system looks: Bracket Single Filers Head of Household Joint Filers 10% $0 to $9,525 $0 to $13,600 $0 to $19,050 12% $9,526 to $38,700 $13,601 to $51,800 $19,051 to $77,400 22.5% $38,701 to $70,000 $51,801 to $60,000 $77,401 to $140,000 25% $70,001 to $160,000 $60,001 to $170,000 $140,001 to $320,000 32.5% $160,001 to $200,000 $170,001 to $200,000 $320,001 to $400,000 35% $200,001 to $500,000 $200,001 to $500,000 $400,001 to $1,000,000 38.5% above $500,000 above $500,000 above $1,000,000 Comparing the three different systems All of these tax bracket systems are marginal, meaning that you don't pay one particular tax rate on all your income; instead, you pay a different rate for each part of your income that falls into a particular bracket. The existing tax code and the Senate Tax Act both have seven different tax brackets; the House Tax Act has only four tax brackets. The tax rates and income ranges for the different types of brackets all vary quite a bit. Image source: Getty Images. How tax brackets work: An example Let's say that you're married and your household income for the year was $117,795 (the average household income in 2014 for married taxpayers filing jointly). Under the current tax code's 2018 brackets, you'd pay 10% income tax on your first $19,050 of income, 15% on your next chunk of income up to $77,400, and 25% on the rest of your income. That means you'd pay a total of $20,756.25 in income taxes for the year. Using the House Tax Act's tax bracket system, you'd instead pay a 12% income tax on the first $90,000 of income and 25% on the rest of your income. This would result in a tax bill of $17,748.75. Finally, using the Senate Tax Act's tax bracket system, you'd pay 10% income tax on your first $19,050 of income, 12% on the next chunk of income up to $77,400, and 22.5% on the rest. The result would be a tax bill of $17,995.88. What to expect next With Senate passage of the bill last weekend, the next step is to reconcile the House and Senate versions of the bill. Only after this is done can the final version pass through Congress and go to the president for his approval. The changes to the tax code won't take effect for the 2017 tax year; when you do your taxes for 2017 in early 2018, you'll use the current system of tax brackets. Then, in the following year, any changes to the tax bracket system will likely take effect. You can check the IRS website at that point to confirm which tax brackets to use; you definitely don't want to use the wrong ones when you do your tax return! The $16,122 Social Security bonus most retirees completely overlook If you're like most Americans, you're a few years (or more) behind on your retirement savings. But a handful of little-known "Social Security secrets" could help ensure a boost in your retirement income. For example: one easy trick could pay you as much as $16,122 more... each year! Once you learn how to maximize your Social Security benefits, we think you could retire confidently with the peace of mind we're all after. Simply click here to discover how to learn more about these strategies.The Motley Fool has a disclosure policy.