X12 837P N301 (Address Information): Format, Values, and Testing Notes
N301 is a free-form text field, which sounds harmless until a test suite only ever feeds it clean, short, single-word street names and never finds out how the rest of the pipeline handles a real address with a suite number jammed into one line or a length near the field's upper bound.
N301 is the first and only required element in an N3 segment on an X12 837P claim — a free-form alphanumeric field holding the primary street address line for the entity named in the preceding NM1 segment, such as a billing provider or subscriber.
What this element contains
Example
N301 (482 OAK ST) carries the primary street address for a synthetic billing provider; N302 holds the suite number separately.
Where this trips people up
Because N301 has no internal structure, some intake systems try to parse a street number and street name back out of it with a regex tuned to whatever sample addresses were in the original test file. Real submitters populate this field with everything from PO boxes to rural route numbers to addresses that already include a suite in a single line, and test data limited to tidy "number plus street name" strings never surfaces the parsing failures those variations cause.