How to create and submit an ACH file?

Question

How can I create an ACH file in a Java application (although the language isn't important) and submit it to be processed? I need to know the format of the ACH file and then what to do with it afterwards. Looking at this question, I see links to external processors. Do I need to use a third party to submit the file?

Creating the file isn't hard (although I can't find details on the format), but then having a file on my hard drive doesn't do any good. If I have to use a third party, what are some good services?

Answer 1

You do need a third party to process the file as you cannot connect to the banks directly. Authorize.Net offers an eCheck service and has an API available that allows you to submit ACH payments.