private function getRegularDueQueryBuilder()
    {
        $qb = $this->createQueryBuilder('o');
        $ex = $qb->expr();

        return $qb
            ->where($ex->andX(
                $ex->eq('o.sample', ':not_sample'),                    // Not sample
                $ex->lt('o.paidTotal', 'o.grandTotal'),                // Paid total lower than grand total
                $ex->notIn('o.invoiceState', ':canceled_or_refunded'), // Not canceled/refunded
                $ex->eq('o.shipmentState', ':shipped'),                // Shipped
                $ex->isNull('o.paymentTerm')                           // Without payment term
            ))
            ->addOrderBy('o.createdAt', 'ASC')
            ->setParameter('not_sample', false)
            ->setParameter('shipped', ShipmentStates::STATE_COMPLETED)
            ->setParameter('canceled_or_refunded', [InvoiceStates::STATE_CANCELED, InvoiceStates::STATE_CREDITED]);
    }
private function getRegularDueQueryBuilder()
    {
        $qb = $this->createQueryBuilder('o');
        $ex = $qb->expr();

        return $qb
            ->where($ex->andX(
                $ex->eq('o.sample', ':not_sample'),                    // Not sample
                $ex->lt('o.paidTotal', 'o.grandTotal'),                // Paid total lower than grand total
                $ex->notIn('o.invoiceState', ':canceled_or_refunded'), // Not canceled/refunded
                $ex->eq('o.shipmentState', ':shipped'),                // Shipped
                $ex->isNull('o.paymentTerm')                           // Without payment term
            ))
            ->addOrderBy('o.createdAt', 'ASC')
            ->setParameter('not_sample', false)
            ->setParameter('shipped', ShipmentStates::STATE_COMPLETED)
            ->setParameter('canceled_or_refunded', [InvoiceStates::STATE_CANCELED, InvoiceStates::STATE_CREDITED]);
    }
Returns the regular due query.

@return QueryBuilder