How to Calculate Federal Income Tax for a Single Person

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Each year, people must file a tax return with the Internal Revenue Service. In order to file the tax return, the taxpayer must be able to calculate his taxes. The IRS provides Form 1040 to report income and make deductions. Using this form allows the taxpayer to properly calculate his taxes for the year. For people with simple taxes, they can fill out Form 1040A or Form 1040EZ.

Step 1

Use Form 1040 Lines 7 through 21 to report income. This income comes in the forms of wages, interest, alimony or other sources. Any time cash flows to you, it will probably qualify as income and needs reporting on Lines 7 through 21. Use the line titles to determine any additional income you may have not remembered. Sources of income come from Forms W-2 and any of the Form 1099s. Add together all the income, and write the number on Form 1040 Line 22.

Step 2

Read through Form 1040 Lines 23 to 35. These are above-the-line deductions. If you think any of them may apply to you, refer to the instructions for Form 1040 for specific information on each deduction. Add the total deduction together, and report the amount on Form 1040 Line 36.

Step 3

Subtract Form 1040 Line 36 from Form 1040 Line 22. Report the amount on Form 1040 Lines 37 and 38. This is your adjusted gross income.

Step 4

Enter $5,700 on Form 1040 Line 40a unless you are itemizing your deductions. Only itemize your deductions if you have more than $5,700 worth of deductions. Itemize deductions on Form 1040 Schedule A. The $5,700 is the 2010 standard deduction for singles. Subtract this amount from the adjusted gross income, and put the result on Form 1040 Line 41.

Step 5

Enter your amount of exemptions on Form 1040 Line 42. You receive a $3,650 exemption automatically. You will receive an addition $3,650 for each instance of having a dependent, being blind or being older than 65. Subtract this amount from the result on Form 1040 Line 41, and put the result on Form 1040 Line 43.

Step 6

Use the Form 1040 tax tables to match the amount of taxable income to the amount of taxes owed for the year (see Resources).

Step 7

Subtract any additional credits you may have. The credits are on Form 1040 Lines 47 to 53. The Form 1040 Instructions have in-depth explanation for each credit. Add any other taxes owed. Other taxes are listed on Form 1040 Line 56 through 59. These taxes include self-employment tax, unreported Social Security and Medicare tax, additional taxes on retirement plans and other taxes. Refer to Form 1040 Instructions for in-depth explanation for applicable other taxes.

Step 8

Subtract any taxes already paid from withholdings on your paycheck. The amount left will be the amount of money you owe or the amount of refund you will receive.