Which payment method requires the maintenance of check stock?

The payment method that requires the maintenance of check stock is paying by check. This involves printing physical checks to send to vendors or payees, which necessitates having a supply of check stock available for use. Each time a check is issued, it draws from this stock, making it essential to manage and restock as needed to ensure there are sufficient checks available for payments.

In contrast, the other payment methods listed do not involve physical checks. For example, paying with Bill.com, making payments via ACH (Automated Clearing House), and batch payments typically utilize electronic systems to facilitate transactions directly from one bank account to another, eliminating the need for physical checks altogether.