Box 30 - Rsvd for NUCC Use

What it is:

Box 30 is reserved for NUCC use. This field was previously used to report “Balance Due.” “Balance Due” does not exist in 5010A1, so this field has been eliminated. This field is now reserved for NUCC use. The NUCC will provide instructions for any use of this field. 

In Therabill:

Therabill no longer puts anything into Box 30.