Tax Brackets

January 26, 2021

We represent the tax brackets as a list of pairs, arranged from high to low:

(define brackets '((100000 0.4) (30000 0.25) (10000 0.1)))

Then the tax calculation is a simple recursion:

(define (tax income brackets)
   (if (null? brackets) 0
     (+ (* (max (- income (caar brackets)) 0) (cadar brackets))
        (tax (min income (caar brackets)) (cdr brackets)))))

Then the tax calculation is a simple recursion:

 > (tax 123456 brackets)
 28882.4

You can run the program at https://ideone.com/T62CTT.

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Posted by programmingpraxis
Filed in Exercises
5 Comments »

5 Responses to “Tax Brackets”

  1. James Smith said
    January 26, 2021 at 4:17 PM

    Perl

    sub tax {
  return ( ( $_[0] >= 10_000  ? 2*($_[0]-10_000)  : 0 ) 
         + ( $_[0] >= 30_000  ? 3*($_[0]-30_000)  : 0 ) 
         + ( $_[0] >= 100_000 ? 3*($_[0]-100_000) : 0 )
         ) / 20; 
}
  2. James Smith said
    January 26, 2021 at 4:18 PM

    Forgot to say – the trick here is to only add the additional tax per bracket – so about 10K is 10%, above 30K is then (25-10)% = 15% and about 100K is then (40-25)% = 15% as well…

  3. Kevin said
    January 27, 2021 at 3:00 AM

    A solution in Racket:

    (define (taxbrk in (brk '(100000 30000 10000 0)) (tax '(0.40 0.25 0.10 0)) (out 0))
  (cond
    ((zero? in) (display (real->decimal-string out)))
    ((> in (car brk)) (taxbrk (car brk) (cdr brk) (cdr tax) (+ out (* (car tax) (- in (car brk))))))
    (else (taxbrk in (cdr brk) (cdr tax) out))))

    Solution in use:

    > (taxbrk 123456)
28882.40
> (taxbrk 0)
0.00
> (taxbrk 10000)
0.00
> (taxbrk 30000)
2000.00
> (taxbrk 100000)
19500.00
> (taxbrk 100200)
19580.00
  4. Daniel said
    January 31, 2021 at 2:11 AM

    Here’s a solution in Python.

    from decimal import Decimal

def tax(income):
    output = Decimal(0)
    for threshold, rate in (100_000, '.40'), (30_000, '.25'), (10_000, '.10'):
        if income >= threshold:
            output += Decimal(rate) * (income - threshold)
            income = threshold
    return output

print(tax(123_456))

    Output:

    28882.40
  5. cagisw said
    March 31, 2021 at 8:29 AM

    Solution in Java:

    public class TaxBrackets {

	public static void main(String[] args) {

		double income = 123456;
		double calculateTax = calculateTax(income);
		System.out.println(calculateTax);
	}

	private static double calculateTax(double income) {
		double totalTax = 0;
		double import1 = 10000;
		double import2 = 30000;
		double import3 = 100000;
		
		if (income <= import1) {
			return totalTax;
		}
		
		if (income > import1 && income <= import2) {
			income = income - import1;
			totalTax = (income * 10) / 100;
			return totalTax;
		}
		
		if (income > import2 && income <= import3) {
			income = income - import2;
			totalTax = ((income * 25) / 100) + 2000;
			return totalTax;
		}
		
		if (income > import3) {
			income = income - import3;
			totalTax = ((income * 40) / 100) + 2000 + 17500;
			return totalTax;
		}
		
		return totalTax;
	}

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