Standard Entry Class Codes. Each ACH application has a unique Standard Entry Class (SEC) Code that identifies a single ACH debit used by an Originator for the conversion of an eligible source document received via the U.S. mail or delivery service, at a lockbox location, or in person at a manned location for the payment of a bill. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.