Remove tax if subtotal is greater than a specific amount

Question

Vers. Magento 1.9.3.8

Due to new duties in Australia I need to add taxes on cart if subtotal is lower than 1000 AUD.

So I'm planing to set a specific tax rate for that country, but it should be applied only if the order subtotal is lower than 1000 AUD.

Any help?

EDIT

Creating a specific tax rate is not what i need. In this way taxes are added to products. They should be applied only to "subtotal < 1000 AUD".

EDIT

To acive this result i've created a new Product Tax Class:

Class Name: Australian GST
Class Id: 6

a new Tax Rate:

Country: Australia
Rate:10

and a new Tax Rule to associate them.

Then I've created an observer fo the event:

sales_quote_collect_totals_before

Observer.php

<?php
class MyCompany_AdditionalTaxes_Model_Observer 
{
    public function addTaxes(Varien_Event_Observer $observer)
    {
        $quote = $observer->getQuote();
        $country = $quote->getShippingAddress()->getCountryId();

        if ($country == 'AU') {
            $currency = $quote->getQuoteCurrencyCode();

            if ($currency == 'AUD') {
                $subtotal = $quote->getSubtotal();
            } else {
                $baseCurrencyCode = Mage::app()->getBaseCurrencyCode();  
                $currencyRates = Mage::getModel('directory/currency')->getCurrencyRates($baseCurrencyCode, array('AUD'));
                $base_subtotal = $quote->getBaseSubtotal();
                $subtotal = $base_subtotal*$currencyRates['AUD'];
            }

            if ($subtotal < 1000) {
                foreach ($quote->getAllItems() as $item){
                    $product = $item->getProduct();
                    $product->setTaxClassId(6);
                }
            }
        }
        return $this;
    }
}

It seems to work fine for cart and checkout page.

If country is Australia and subtotal is lower than 1000AUD tax rate of 10% is applied. In all other cases normal configuration of taxes is applied.

I've still got problem with PayPal Express Checkout.

The callbak API hits shippingOptionsCallbackAction()

public function shippingOptionsCallbackAction()
{
    try {
        $quoteId = $this->getRequest()->getParam('quote_id');
        $this->_quote = Mage::getModel('sales/quote')->load($quoteId);
        $this->_initCheckout();
        $response = $this->_checkout->getShippingOptionsCallbackResponse($this->getRequest()->getParams());
        $this->getResponse()->setBody($response);
    } catch (Exception $e) {
        Mage::logException($e);
    }
}

but when quote is loaded with

Mage::getModel('sales/quote')->load($quoteId);

seems to ignore the observer

Answer 1

I had to fire

sales_quote_address_collect_totals_before

instead of

sales_quote_collect_totals_before

and made some change ti the observer

<?php
class MyCompany_AdditionalTaxes_Model_Observer 
{
    public function addTaxes(Varien_Event_Observer $observer)
    {
        $quoteAddress = $observer->getQuoteAddress()->getQuote();
        $quote = Mage::getModel('sales/quote')->load($quoteAddress->getId());;
        $country = $quoteAddress->getShippingAddress()->getCountryId();

        if ($country == 'AU') {
            $currency = $quote->getQuoteCurrencyCode();

            if ($currency == 'AUD') {
                $subtotal = $quote->getSubtotal();
            } else {
                $baseCurrencyCode = Mage::app()->getBaseCurrencyCode();  
                $currencyRates = Mage::getModel('directory/currency')->getCurrencyRates($baseCurrencyCode, array('AUD'));
                $base_subtotal = $quote->getBaseSubtotal();
                $subtotal = $base_subtotal*$currencyRates['AUD'];
            }

            if ($subtotal < 1000) {
                foreach ($quoteAddress->getAllItems() as $item){
                    $product = $item->getProduct();
                    $product->setTaxClassId(6);
                }
            }
        }
        return $this;
    }
}