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US Federal Income Tax calculator in javascript
// Weekly Employee Income Withholding Calculator by GitHub#Liath
// Based on IRS Circular E - http://www.irs.gov/pub/irs-pdf/p15.pdf
// Per the "Percentage Method"
var w = {
s : { // Single
0 : { p : 0, s : 0 },
44 : { p: 0.1, s: 0 },
222 : { p: 0.15, s: 17.8 },
764 : { p: 0.25, s: 99.1 },
1789 : { p: 0.28, s: 355.35 },
3685 : { p: 0.33, s: 886.23 },
7958 : { p: 0.35, s: 2296.32 },
7990 : { p: 0.396, s: 2307.52 }
},
m : { // Married
0 : { p : 0, s : 0 },
165 : { p : 0.1, s : 0 },
520 : { p : 0.15, s : 35.5 },
1606 : { p : 0.25, s : 198.4 },
3073 : { p : 0.28, s : 565.15 },
4597 : { p : 0.33, s : 991.87 },
8079 : { p : 0.35, s : 2140.93 },
9105 : { p : 0.396, s : 2500.03 }
}
},
ba = 76.9, // 1 Allowance
c = function(m, a, g) { // Returns Federal Income Tax amount (Married, Allowances, Gross Income)
g -= (ba*a); // Pay after allowances
var b = Object.keys(w[(m==1) ? 'm' : 's']); //Married?
for (var i = 0; i < b.length; i++) { // Find bracket
if (b[i] > g) {
g -= b[i-1]; // Get taxable income
b = w[(m==1) ? 'm' : 's'][b[i-1]]; // Set bracket
return ((b.p*(g)) + b.s); // Taxable income * Tax Rate + Base Tax, per IRS Circular E table 5
}
}
}
@Kpatton8807

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Kpatton8807 commented Mar 13, 2017

I'm so confused on this one I can't get it to work for the life of me can someone please Help

@Liath

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Liath commented May 31, 2017

So, if you're single with one allowance and you make $1000 a week you would run c(0, 1, 1000). 0 for single, 1 is the allowances, and $1000/week. Should result in 138.875.

@i3o

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i3o commented Apr 26, 2018

Thank you for this, Liath! I have websites that rely on this code, so I forked it to keep it updated each year: https://gist.github.com/axcviii/502ef703ec727507e5cb1a5232df7fc7 (currently 2018 rates).

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