public function checkPaidAmount()
 {
     if (false == $this->getInvoiceId()) {
         return false;
     }
     if (false == $this->getAmount()) {
         return false;
     }
     $objDataInvoice = new GSALES_DATA_INVOICE();
     $objInvoice = $objDataInvoice->getInvoiceByIdWithoutUserCheck($this->getInvoiceId(), true);
     if ($objInvoice->getOpenAmount() == $this->getAmount()) {
         return true;
     }
     if (number_format($this->getAmount(), 2) == number_format($objInvoice->getOpenAmount(), 2)) {
         return true;
     }
     // to compare calculated floats (currency) :(
     return false;
 }