The account number is for the user's personal reference and is not required by the NACHA standard. I hadn't used that optional field in prior hand-coded NACHAs and, when I omitted it from the payment info, it silently failed to add the payment. In the interest of easy AB comparison between the hand-coded version and this library's version, I removed the strict requirement for the field.

Clearly this is an opinion matter. My opinion is since the NACHA standard considers it optional, so should the library.