Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE INVOICES (payment_method_code VARCHAR)
### Question:
What is the payment method code used by the most orders?
### Answer:
SELECT payment_method_code FROM INVOICES GROUP BY payment_method_code ORDER BY COUNT(*) DESC LIMIT 1