Again, under "Tax Imposed"
http://www.law.cornell.edu/uscode/text/26/1
a) Married individuals filing joint returns and surviving spouses
There is hereby imposed on the taxable income of—
(1) every married individual (as defined in section 7703) who makes a single return jointly with his spouse under section 6013, and
(2) every surviving spouse (as defined in section 2 (a)),
a tax determined in accordance with the following table:
If taxable income is: The tax is:
Not over $36,900 15% of taxable income.
Over $36,900 but not over $89,150 $5,535, plus 28% of the excess over $36,900.
Over $89,150 but not over $140,000 $20,165, plus 31% of the excess over $89,150.
Over $140,000 but not over $250,000 $35,928.50, plus 36% of the excess over $140,000.
Over $250,000 $75,528.50, plus 39.6% of the excess over $250,000.
(b) Heads of households
There is hereby imposed on the taxable income of every head of a household (as defined in section 2 (b)) a tax determined in accordance with the following table:
If taxable income is: The tax is:
Not over $29,600 15% of taxable income.
Over $29,600 but not over $76,400 $4,440, plus 28% of the excess over $29,600.
Over $76,400 but not over $127,500 $17,544, plus 31% of the excess over $76,400.
Over $127,500 but not over $250,000 $33,385, plus 36% of the excess over $127,500.
Over $250,000 $77,485, plus 39.6% of the excess over $250,000.
(c) Unmarried individuals (other than surviving spouses and heads of households)
There is hereby imposed on the taxable income of every individual (other than a surviving spouse as defined in section 2 (a) or the head of a household as defined in section 2 (b)) who is not a married individual (as defined in section 7703) a tax determined in accordance with the following table:
If taxable income is: The tax is:
Not over $22,100 15% of taxable income.
Over $22,100 but not over $53,500 $3,315, plus 28% of the excess over $22,100.
Over $53,500 but not over $115,000 $12,107, plus 31% of the excess over $53,500.
Over $115,000 but not over $250,000 $31,172, plus 36% of the excess over $115,000.
Over $250,000 $79,772, plus 39.6% of the excess over $250,000.
(d) Married individuals filing separate returns
There is hereby imposed on the taxable income of every married individual (as defined in section 7703) who does not make a single return jointly with his spouse under section 6013, a tax determined in accordance with the following table:
If taxable income is: The tax is:
Not over $18,450 15% of taxable income.
Over $18,450 but not over $44,575 $2,767.50, plus 28% of the excess over $18,450.
Over $44,575 but not over $70,000 $10,082.50, plus 31% of the excess over $44,575.
Over $70,000 but not over $125,000 $17,964.25, plus 36% of the excess over $70,000.
Over $125,000 $37,764.25, plus 39.6% of the excess over $125,000.