Module: Taxger::Einkommensteuer

Extended by:
Einkommensteuer
Included in:
Einkommensteuer
Defined in:
lib/taxger/einkommensteuer.rb

Defined Under Namespace

Classes: Error, Result

Constant Summary collapse

F = 
10**-8
ZONES = 
{
  # Values are taken from this table:
  # https://de.wikipedia.org/wiki/Einkommensteuer_(Deutschland)#Entwicklung_der_Parameter
  # Non-existent parameters for E(i) with i > 3 have to be replaced with nil 
  # Non-existent parameters for a(i) with i > 2 have to be 0.
  '2010' => [
     #   E(0),   a(1) * F,   b(1),        0
     [  8_003, 912.17 * F,   0.14,        0],

     #   E(1),   a(2) * F,   b(2),     S(1)
     [ 13_469, 228.74 * F, 0.2397,     1038],

     #   E(2),  a(3) (=0),   b(3),     S(2)
     [ 52_881,          0,   0.42,   14_038.5],

     #   E(3),  a(4) (=0),   b(4),     S(3)
     [250_730,          0,   0.45,   97_134.5]
  ],

  # no change from 2010
  '2011' => [
     [  8_003, 912.17 * F,   0.14,        0],
     [ 13_469, 228.74 * F, 0.2397,     1038],
     [ 52_881,          0,   0.42,   14_038.5],
     [250_730,          0,   0.45,   97_134.5]
  ],

  # no change from 2010
  '2012' => [
     [  8_003, 912.17 * F,   0.14,        0],
     [ 13_469, 228.74 * F, 0.2397,     1038],
     [ 52_881,          0,   0.42,   14_038.5],
     [250_730,          0,   0.45,   97_134.5]
  ],

  '2013' => [
     [  8_130, 933.70 * F,   0.14,        0],
     [ 13_469, 228.74 * F, 0.2397,     1014],
     [ 52_881,          0,   0.42,   -8196 + 0.42 * 52_881],
     [250_730,          0,   0.45,   -15718 + 0.45 * 250_730]
  ],

  '2014' => [
     [  8_354, 974.58 * F,   0.14,        0],
     [ 13_469, 228.74 * F, 0.2397,      971],
     [ 52_881,          0,   0.42,   -8239 + 0.42 * 52_881],
     [250_730,          0,   0.45,   -15761 + 0.45 * 250_730]
  ],

  '2015' => [
     [  8_472,  997.6 * F,   0.14,        0],
     [ 13_469, 228.74 * F, 0.2397,   948.68],
     [ 52_881,          0,   0.42,   13_949],
     [250_730,          0,   0.45,   97_045]
  ],

  '2016' => [
     [  8_652, 993.62 * F,   0.14,        0],
     [ 13_669, 225.40 * F, 0.2397,   952.48],
     [ 53_665,          0,   0.42,     -8394.14 + 0.42 * 53_665],
     [254_447,          0,   0.45,   -16027.52 + 0.45 * 254_447]
  ],
}

Instance Method Summary collapse

Instance Method Details

#calculate(year, income) ⇒ Object 



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# File 'lib/taxger/einkommensteuer.rb', line 81

def calculate(year, income)
  if !ZONES[year.to_s]
    raise Einkommensteuer::Error.new("No data available for year #{year}")
  end

  income = income * 0.01
  ZONES[year.to_s].reverse.each do |zone|
    (zone_start, a, b, c) = zone
    if income >= zone_start + 1
      taxable = income - zone_start
      tax = (a * (taxable ** 2) + b * taxable + c).to_i * 100

      # Vereinfachte Berechnung des Solidaritätszuschlagsfreibetrags:
      # Nicht gültig für Steuerklasse III (162 EUR statt 81 EUR) und abweichend,
      # wenn Lohnsteuer in verschiedenen Monaten jeweils unter- und überhalb der
      # Grenze lag.
      solz = tax > 81_00 * 12 ? (tax * 0.055).to_i : 0
      return Result.new(tax, solz)
    end
  end
  Result.new(0, 0)
end