Hi,
By default, the invoice is available after the payment. And that's why the bank information is not included in the invoice.
It's however available at the end of the checkout, the email notifications, and if you click on the pay now button of an order not yet paid, if the payment method selected is bank transfer.
To modify the invoice available to you in the backend, you can edit the file order / invoice via the menu Display>Views.
There, you can add custom thank you messages at the end of the view file.
And regarding the bank transfer information you entered in your payment method, you can use such code:
<?php
if(in_array($this->element->order_payment_method, array('banktransfer', 'check', 'purchaseorder'))) {
$amount = $currencyHelper->format($this->element->order_full_price, $this->element->order_currency_id);
$paymentClass = hikashop_get('class.payment');
$payment = $paymentClass->get($this->element->order_payment_id);
$information = $payment->payment_params->information;
if(preg_match('#^[a-z0-9_]*$#i',$information)){
$information = JText::_($information);
}
if($this->element->order_payment_method=='banktransfer'){
echo '<p>' . JText::sprintf('PLEASE_TRANSFERT_MONEY',$amount).'<br/>'.$information.'<br/>'.JText::sprintf('INCLUDE_ORDER_NUMBER_TO_TRANSFER',$this->element->order_number) . '</p>';
}elseif($this->element->order_payment_method=='check'){
echo '<p>' . JText::sprintf('PLEASE_SEND_CHECK',$amount).'<br/>'.$information.'<br/>'.JText::sprintf('INCLUDE_ORDER_NUMBER_TO_CHECK',$this->element->order_number) . '</p>';
}elseif($this->element->order_payment_method=='purchaseorder'){
echo '<p>' . JText::sprintf('PLEASE_SEND_PURCHASEORDER',$amount).'<br/>'.$information.'<br/>'.JText::sprintf('INCLUDE_ORDER_NUMBER_TO_PURCHASEORDER',$this->element->order_number) . '</p>';
}
}
?>
The code is a copy/paste (and adapted) from the order creation notification (which is sent to the customer and already contain that information) email's preload code you can find in the menu System>Emails.