/*
* [AmericanTaxTable.java]
*
* Summary: Does the math to compute American state and county sales tax.
*
* Copyright: (c) 1999-2017 Roedy Green, Canadian Mind Products, http://mindprod.com
*
* Licence: This software may be copied and used freely for any purpose but military.
* http://mindprod.com/contact/nonmil.html
*
* Requires: JDK 1.8+
*
* Created with: JetBrains IntelliJ IDEA IDE http://www.jetbrains.com/idea/
*
* Version History:
* 2.7 2008-06-01 add WI support for counties.
* 2.8 2008-06-01 add AZ support for counties and cities
* 2.9 2010-05-10 update state tax tables, better rounding, massive refactoring.
* 3.0 2010-12-08 update Alabama and Tennessee tax tables.
* 3.1 2010-12-09 update California, Georgia, Illinois, Missouri and North Carolina tax tables.
* 3.2 2010-12-11 updated Arizona, Colorado, Hawaii, Iowa, Ohio, Texas, Washington, Wisconsin tax tables.
* 3.3 2010-12-12 updated Florida, Louisiana, New York, Wyoming. New streamlined PrepStateBase skeleton.
* 3.4 2010-12-14 updated Arkansas, Kansas, South Carolina, Oklahoma.
* 3.5 2010-12-15 updated Nebraska, Nevada, North Dakota, Utah
* 3.6 2010-12-17 updated Alabama. Can look up city without needing to know county.
* 3.7 2010-12-18 updated South Dakota, Minnesota, New Mexico
* 3.8 2010-12-19 update Idaho, Vermont.
*/
package com.mindprod.americantax;
import java.util.Vector;
import static java.lang.System.*;
/**
* Does the math to compute American state and county sales tax.
*
* AmericanTax.java is the GUI shell portion, AmericanTaxTable.java are the driving tables
*
* Computes American Sales taxes. HowToProcess American Sales taxes are computed: We currently calculate only the state
* sales tax, not city or use taxes. It is computed as a percentage of the sale, with a different rate for each state.
* If vendor and buyer are in the same state, the tax is applicable, otherwise no tax is due. This may change as states
* realise how much tax they are losing to out of state Internet sales and purchases. Already Ohio residents are
* supposed to declare out of state purchases on which they paid no sales tax on their income tax returns.
*
* When Vendor and buyer are in the same state, then it depends if the goods are delivered what the sales tax district
* jurisdiction is, at least in Colorado. For example, if I pick up something at a store, I pay the vendor's local tax.
* If I pay for a refrigerator at a store, but if I have it delivered to my house, I pay the tax for the district of my
* house. Different sorts of goods are eligible taxation in different states. The exemption rules are complicated. New
* York, Colorado and California have combined sales/use taxes at the county and city level. Probably other states do as
* well.
*
* Alabama is weird,
* Florida, Georgia, Nebraska, Nevada, Ohio, South Carolina, Wisconsin have no city taxes,
* Nebraska, North Dakota, South Dakota has no county info yet.
* Illinois has flat file raw input. Sort out negative tax items.
*
* @author Roedy Green, Canadian Mind Products
* @version 3.8 2010-12-19 update Idaho, Vermont
* @see PrepAlabama
* @see PrepArizona
* @see PrepArkansas
* @see PrepCalifornia
* @see PrepColorado
* @see PrepFlorida
* @see PrepGeorgia
* @see PrepIdaho
* @see PrepIllinois
* @see PrepIowa
* @see PrepKansas
* @see PrepLouisiana
* @see PrepMinnesota
* @see PrepMissouri
* @see PrepNebraska
* @see PrepNevada
* @see PrepNewMexico
* @see PrepNewYork
* @see PrepNorthCarolina
* @see PrepNorthDakota
* @see PrepOhio
* @see PrepOklahoma
* @see PrepSouthCarolina
* @see PrepSouthDakota
* @see PrepTennessee
* @see PrepTexas
* @see PrepUtah
* @see PrepVermont
* @see PrepWashington
* @see PrepWisconsin
* @see PrepWyoming
* @since 1999
*/
public final class AmericanTaxTable
{
/*
* http://en.wikipedia.org/wiki/Sales_taxes_in_the_United_States
* For a map showing state sales taxes: see http://thestc.com/STrates.stm
* The Wikipedia has an entry on sales takes. It is usually the most up to date. http://en.wikipedia
* .org/wiki/Sales_taxes_in_the_United_States
* For up-to-Date state tax information, see: http://www.salestaxinstitute.com They sell a book explaining sales
* takes.
* For links to individuals state agencies see: http://dir.yahoo
* .com/Government/U_S__Government/Taxes/State_Tax_Agencies/
* Commercial tax rate database.
* http://www.taxdatasystems.com/
* For a list of counties (no taxes) see http://en.wikipedia.org/wiki/List_of_U.S._counties_in_alphabetical_order
* Cities
* STATES WITH SIMPLE RULES
* In Virginia are their own counties.
* For Virginia sale taxes: http://www.tax.virginia.gov/site.cfm?alias=SalesUseTax#Retail
* 4% state tax and 1% local
* for Mississippi http://www.mstc.state.ms.us/taxareas/sales/rates.htm
* has state tax rate of Mississippi has a 7% state sales tax.
* No local tax other than Lee,Tupelo at 0.25% tax
* STATES THAT LEVY A STATE-WIDE SALES TAX ONLY:
* Connecticut
* Indiana
* Kentucky
* Maine
* Maryland
* Massachusetts
* Michigan
* New Jersey
* Rhode Island
* Virginia
* West Virginia
* State, county and locaaltax tables are complete for all states.
* If you have the information, please pass it along.
* http://www.zip2tax.com/ zip code to tax.
*/
/**
* debugging switch. Turns on display code in main test driver.
*/
private static final boolean DEBUGGING = false;
/**
* purely static class. Hide the constructor.
*/
private AmericanTaxTable()
{
}
/**
* generic compute usome tax. Done internally with longs to precisely round taxes to correct penny.
*
* @param rate 7% = 70,000 tax rate
* * @param saleAmount amount on which tax is calculated in dollars.
* @param saleAmount in dollars.
*
* @return tax in dollars
*/
private static double calcTax( int rate, double saleAmount )
{
final long saleInPennies = ( long ) ( saleAmount * 100 + 0.5 );
// scale = 2 (pennies) 2 (percent) 4 (fraction)
final long taxScaled = saleInPennies * rate;
// round to pennies and return dollars.
final long taxInPennies = ( taxScaled + 500000 ) / 1000000;
// return tax in dollars
return taxInPennies / 100.0d;
}
/**
* Round dollar values to penny.
*
* @param dollars amount in fractional dollars
*
* @return dollars rounded to the nearest penny.
*/
private static double dollarRounded( double dollars )
{
// 0.105 should be rounded up to 0.11, however 0.105 might be represented as 0.104999999 because of
// binary-decimal conversion problems.
return Math.rint( dollars * 100.0d ) / 100d;
}
/**
* Calculate the district without state tax
*
* @param districtItem which district.
* @param saleAmount amount on which tax is calculated.
*
* @return sales tax due in pennies. Invalid states will generate 0 result. Deliberately invalid states can be used
* to denote out of country.
*/
public static double calcDistrictSalesTax( DistrictItem districtItem, double saleAmount )
{
return calcTax( districtItem.getDistrictTaxRate(), saleAmount );
}
/**
* Calculate the sale amount, working backwards from the Total Payable. When you calculate forward again you may be
* off a penny or two from the original total payable. This is unavoidable, nothing to do with the program. This
* method gives you the closest possible value.
*
* @param district information on district we are computing taxes for.
* @param totalPayable total including all taxes.
*
* @return sale amount after you remove the taxes from the totalPayable.
* @noinspection SameParameterValue, WeakerAccess
*/
public static double calcSaleAmount( DistrictItem district, double totalPayable )
{
// make estimate, then tweak by a penny to find best match to totalPayable.
double saleAmount = dollarRounded( totalPayable / ( 1.0 + district.getTotalTaxRate() / 1000000d ) );
// see how good an estimate we have
double bestDiff = 999999.;
double bestSaleAmount = saleAmount;
while ( true )
{
final double totalPayable2 = calcTotalPayable( district, saleAmount );
final double diff = totalPayable2 - totalPayable;
if ( Math.abs( diff ) >= bestDiff )
{
// we are doing worse that previously. We have overshot,
return bestSaleAmount;
}
else
{
// this is the best so far.
bestSaleAmount = saleAmount;
bestDiff = Math.abs( diff );
}
if ( diff == 0 )
{
return bestSaleAmount;
}
else if ( diff > 0 )
{
// estimate for saleAmount was too large
// try an estimate 1 penny smaller to see if it works better.
saleAmount -= .01;
}
else
{
// estimate for saleAmount was too small
// try an estimate 1 penny bigger to see if it works better.
saleAmount += .01;
}
saleAmount = dollarRounded( saleAmount );
}
}
/**
* Calculate the state tax.
*
* @param districtItem which district.
* @param saleAmount amount on which tax is calculated.
*
* @return sales tax due in dollars. Invalid states will generate 0 result. Deliberately invalid states can be used
* to denote out of country.
*/
public static double calcStateSalesTax( DistrictItem districtItem,
double saleAmount )
{
return calcTax( districtItem.getStateTaxRate(), saleAmount );
}
/**
* Calculate the state+district tax.
*
* @param districtItem which district.
* @param saleAmount amount on which tax is calculated.
*
* @return total payable amount + tax . Invalid states will generate 0 result. Deliberately invalid states can be
* used
* to denote out of country.
*/
public static double calcTotalPayable( DistrictItem districtItem,
double saleAmount )
{
return calcTax( districtItem.getTotalTaxRate(), saleAmount ) + saleAmount;
}
/**
* Calculate the state+district tax.
*
* @param districtItem which district.
* @param saleAmount amount on which tax is calculated.
*
* @return sales tax . Invalid states will generate 0 result. Deliberately invalid states can be used
* to denote out of country.
*/
public static double calcTotalSalesTax( DistrictItem districtItem,
double saleAmount )
{
return calcTax( districtItem.getTotalTaxRate(), saleAmount );
}
/**
* Test driver
*
* @param args not used
*/
public static void main( String[] args )
{
if ( DEBUGGING )
{
Vector states = StateItem.getStateChoices();
for ( StateItem state : states )
{
out.println( state );
Vector districts = state.getDistrictItems();
for ( DistrictItem district : districts )
{
out.print( district + ":" );
}
}
}
} // end main
}