Danish tax calculations for Google sheets

dk-tax.js

function DK_TAX_PARSE_OPTIONS(opts) {
  var options = {
    hasChildren: true,           // Do you receive "børnepenge"?
    isFamily: true,              // Are you married (and your spouse without income)?
    interests: 44256,            // Deductible interests paid (typically on a mortgage)
    churchTax: 0.00867,          // Set your church tax rate here, if you are a member of the church. Otherwise set to 0.0
    municipalityTaxRate: 0.24926 // Find you tax rate here: https://www.skm.dk/skattetal/satser/kommuneskatter
  };
  var applyOption = function(key, value) {
    var key = key.trim();
    if (typeof value == "string") {
      var value = value.trim();
      if (key == "hasChildren" || key == "isFamily") {
        options[key] = value.toLowerCase() == "true";
      } else if (key == "churchTax" || key == "municipalityTaxRate") {
        options[key] = parseFloat(value);
      } else {
        options[key] = parseInt(value);
      }
    } else {
      options[key] = value;
    }
  };
  if (opts) {
    if (typeof opts.forEach != "undefined") {
      opts.forEach(function(row) {
        applyOption(row[0], row[1]);
      });
    } else {
      opts.split(";").forEach(function(pair) {
        var tmp = pair.split("=");
        applyOption(tmp[0], tmp[1]);
      });
    }
  }
  return options;
}

/**
 * Calculate the remainder after PI taxes.
 * + gross       The gross income
 * + grossOffset Previously taxed gross amount
 *
 * Antagelser (2019)
 *
 * AM bidrag (bruttoskat) 8%
 * Personfradrag 2 x 46.200
 * Bundskat 12,16%
 * Topskat over 513.400 15%
 * Kommuneskat 24,926%
 * Børnepenge over 782.600 2%
 * Kirkeskat 0,867%
 */
function DK_TAX_PERSONAL_INCOME(gross, grossOffset, options) {
  var kommuneskat, bundskat, topskat, topskat_limit, toptopskat, toptopskat_limit, labour_deductions, deduction_limit, taxable, toptopskat_taxable, topskat_taxable, bundskat_taxable, net, netOffset;

  options = DK_TAX_PARSE_OPTIONS(options);

  if (typeof(grossOffset) == "number") {
    netOffset = DK_TAX_PERSONAL_INCOME(grossOffset);
  } else {
    grossOffset = 0;
    netOffset = 0;
  }
  gross += grossOffset;
  
  kommuneskat = options.municipalityTaxRate;
  bundskat = kommuneskat + 0.1213 + options.churchTax;
  topskat = Math.min(bundskat + 0.155, 0.5205);
  topskat_limit = 513400;
  toptopskat = topskat + 0.02;
  toptopskat_limit = options.hasChildren ? 782600 : 100000000;
  labour_deductions = 37200 + 2100; // Andre fradrag: Beskæftigelse, Job
  deduction_limit = 46200 * (options.isFamily ? 2 : 1);       // Personfradrag
  deduction_limit += options.interests * 0.336;  // Fradrag for renter på lån
  deduction_limit += labour_deductions * 0.249;

  taxable = gross * 0.92;

  if (taxable <= deduction_limit) {
    return Math.round(taxable - netOffset);
  }

  taxable -= deduction_limit;
  toptopskat_taxable = Math.max(0, taxable - toptopskat_limit);
  topskat_taxable = Math.min(Math.max(0, taxable - topskat_limit), toptopskat_limit - topskat_limit);
  bundskat_taxable = taxable - (topskat_taxable + toptopskat_taxable);

  net = deduction_limit;
  net += bundskat_taxable * (1.0 - bundskat);
  net += topskat_taxable * (1.0 - topskat);
  net += toptopskat_taxable * (1.0 - toptopskat);

  return Math.round(net - netOffset);
}

/**
 * Calculate the remainder after business taxes.
 * + gross  The gross income
 */
function DK_TAX_BUSINESS(gross) {
  return Math.round(gross * (1 - 0.22));
}

/**
 * Calculate the remainder after PAL tax on ratepension gains.
 * + gross  The gross gains
 */
function DK_TAX_RATEPENSION(gross) {
  return Math.round(gross * (1 - 0.153));
}

/**
 * Calculate the remainder tax on stock gains.
 * + gross  The gross gains
 */
function DK_TAX_STOCK(gross, options) {
  var limit, high, low;
  
  options = DK_TAX_PARSE_OPTIONS(options);
  limit = 54000 * (options.isFamily ? 2 : 1);
  high = Math.max(0, gross - limit);
  low = gross - high;

  return Math.round((low * (1 - 0.27)) + (high * (1 - 0.42)));
}

/**
 * Find the gross required to provide a given net
 */
function DK_TAX_PERSONAL_INCOME_REVERSE(net) {
  var result, gross, increment;
  increment = 10000;
  gross = increment;
  while (true) {
    result = DK_TAX_PERSONAL_INCOME(gross);
    if (result >= net) {
      return gross;
    }
    gross += increment;
  }
}

/**
 * Find the gross required to provide a given net
 */
function DK_TAX_STOCK_REVERSE(net, options) {
  var limit, net_limit, high, low;
  
  options = DK_TAX_PARSE_OPTIONS(options);
  limit = 54000 * (options.isFamily ? 2 : 1);

  net_limit = limit * (1 - 0.27);
  
  high = Math.max(0, net - net_limit);
  low = net - high;

  return Math.round((low / (1 - 0.27)) + (high / (1 - 0.42)));
}