public function geAdyenPaymentInvoiceFeeAmount()
    {
        $fee = null;
        $creditmemo = $this->getSource();
        if ($creditmemo) {
            if ($creditmemo->getPaymentFeeAmount() !== null) {
                $source = $this->getSource();
                $taxConfig = Mage::getSingleton('adyen_fee/tax_config');

                if ($taxConfig->displaySalesPaymentFeeInclTax($source->getOrder()->getStoreId())) {
                    $fee = $creditmemo->getPaymentFeeAmount() + $creditmemo->getPaymentFeeTax();
                } else {
                    $fee = $creditmemo->getPaymentFeeAmount();
                }

                $fee = Mage::app()->getStore()->roundPrice($fee);
            }
        }

        return $fee;
    }