how to update tax amount with custom price in magento 2

Question

HOW TO UPDATE TAX WITH CUSTOM VALUE IN CART OR CHECKOUT.My requirement was when customer click add to cart and he move to cart that time i want to update tax with some API so do the needful.

Answer 1

One approach is :

You can try to overide the default collect total tax function.

Add this dependency :

<preference for="Magento\Tax\Model\Sales\Total\Quote\Tax" type="Vendor\Module\Model\Tax\Sales\Total\Quote\Tax"/>

Create you own Quote Tax Collection function based on native one.

Add your logic inside the collect function.

Example :

/**
 * Custom Collect tax totals for quote address
 *
 * @param Quote $quote
 * @param ShippingAssignmentInterface $shippingAssignment
 * @param Address\Total $total
 * @return $this
 * @throws RemoteServiceUnavailableException
 */
public function collect(
    Quote $quote,
    ShippingAssignmentInterface $shippingAssignment,
    Address\Total $total
) {
    $address = $shippingAssignment->getShipping()->getAddress();

    $storeId = $quote->getStoreId();

    if ($this->doNotUseCustomTax()
    ) {
        return parent::collect($quote, $shippingAssignment, $total);
    }

    $this->processCustomTax($quote);

    return $this;
}

Answer 2

  public function collect(
    \Magento\Quote\Model\Quote $quote,
    \Magento\Quote\Api\Data\ShippingAssignmentInterface $shippingAssignment,
    \Magento\Quote\Model\Quote\Address\Total $total
) {
    
    $this->clearValues($total);
    if (!$shippingAssignment->getItems()) {
        return $this;
    }

    $x= $quote->getItems();
    if (isset($x)) {
        foreach ($x as $item) {
            $g = $item;
            $y = $item->getSku();
            $y = $item->getProductId();
        }
    }
    
    $baseTaxDetails = $this->getQuoteTaxDetails($shippingAssignment, $total, true);
    $taxDetails = $this->getQuoteTaxDetails($shippingAssignment, $total, false);

    //Populate address and items with tax calculation results
    $itemsByType = $this->organizeItemTaxDetailsByType($taxDetails, $baseTaxDetails);
    if (isset($itemsByType[self::ITEM_TYPE_PRODUCT])) {
        $this->processProductItems($shippingAssignment, $itemsByType[self::ITEM_TYPE_PRODUCT], $total);
    }

    if (isset($itemsByType[self::ITEM_TYPE_SHIPPING])) {
        $shippingTaxDetails = $itemsByType[self::ITEM_TYPE_SHIPPING][self::ITEM_CODE_SHIPPING][self::KEY_ITEM];
        $baseShippingTaxDetails =
            $itemsByType[self::ITEM_TYPE_SHIPPING][self::ITEM_CODE_SHIPPING][self::KEY_BASE_ITEM];
        $this->processShippingTaxInfo($shippingAssignment, $total, $shippingTaxDetails, $baseShippingTaxDetails);
    }

    //Process taxable items that are not product or shipping
    $this->processExtraTaxables($total, $itemsByType);

   $total->setTaxAmount(2000);
   $total->setGrandTotal($total->getBaseGrandTotal()+2000);
   
    //Save applied taxes for each item and the quote in aggregation
    $this->processAppliedTaxes($total, $shippingAssignment, $itemsByType);

    if ($this->includeExtraTax()) {
        $total->addTotalAmount('extra_tax', $total->getExtraTaxAmount());
        $total->addBaseTotalAmount('extra_tax', $total->getBaseExtraTaxAmount());
    }

    return $this;
}

The above code works for me.