Sanjoy Roy

[MCM, MCP, SCJP] – Senior PHP Programmer

Modify Magento TAX Calculation

Change the following file: magento\app\code\core\Mage\Tax\Model\Calculation.php

     * Calculate rated tax abount based on price and tax rate.
     * If you are using price including tax $priceIncludeTax should be true.
     * @param   float $price
     * @param   float $taxRate
     * @param   boolean $priceIncludeTax
     * @return  float
    public function calcTaxAmount($price, $taxRate, $priceIncludeTax=false, $round=true)
        $taxRate = 10;
		$taxRate = $taxRate/100;
		$this->insertInLog('taxRate', $taxRate);
		$this->insertInLog('price', $price);
        if ($priceIncludeTax) {
            $amount = $price*(1-1/(1+$taxRate));
        } else {
            $amount = $price*$taxRate;
		$this->insertInLog('Amount', $amount);
        if ($round) {
            return $this->round($amount);
        } else {
            return $amount;

     * Insert in to Log Table. It helps to trace and stores in table
     * @param   varchar $title
     * @param   varchar $desc

	function insertInLog($title, $desc){		
		$sql = "insert into log_tbl values('".$title."', '".$desc."', '".date("Y-m-d h:i:s")."')";

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