Debit cards, also called "check cards," enable purchasers to make electronic purchases debited directly against their bank accounts. Point-of-sale debit transactions — also known as POS debit transactions — come in two main varieties: online debit and offline debit. Online debit, or ATM-debit, transactions requiring a PIN number are routed directly to the customer's bank, which locks in the funds in real time. Offline debit transactions are routed through the interchange system, similar to a credit card purchase. Merchant service providers charge merchants a percentage fee to process offline debit transactions, while online debit transactions typically cost a flat rate per transaction.

Open a business checking account. You must have a business checking account for the merchant services company to route credit and debit payments to you.

Contact a merchant services provider. Banks often contract with merchant services providers to provide this service for the merchant banking customers, or you can contract with one independently.

Purchase or lease a credit card terminal or POS (point-of-sale) software program. You need a phone line to process transactions as well, though low-volume merchants frequently have one phone line for their telephone and merchant services transactions.

Purchase or lease a PIN pad, a device that allows customers to enter their PIN transactions. You don't need a PIN pad to run a debit card such as a credit card, but you must use a PIN pad to run the transaction as an online transaction, which may save you a good deal of money. For example, a merchant paying 2 percent on a $50 average ticket size would pay $1 per transaction. By obtaining a PIN pad, the same merchant may run a $50 transaction as an online debit for 40 cents or less.