R04: Invalid Account Number Structure
The account number fails the receiving bank's structural validation.
| Code | R04 |
|---|---|
| Official reason | Invalid Account Number Structure |
| Applies to | Credits and debits |
| Return deadline | 2 banking days |
What R04 means
Distinct from R03: the bank did not merely fail to find the account, it rejected the number's shape — wrong length, illegal characters, or a failed check digit. Spreadsheet formatting is the usual culprit, especially numbers stored as numeric values and rendered in scientific notation.
What to do next
Re-check the source data as text, not as numbers. A file that produces R04 across many rows almost always has a column-formatting problem rather than many bad recipients.
Can this happen on a file from this generator?
Yes. R04 can come back on a credit file, so it is worth guarding against. Verify account details with a zero-dollar prenote before the first live payment, and check the file's structure with the ACH file validator before you upload it to your bank.
Other return codes
R01, R02, R03, R06, R07, R08, R09, R10, R11, R16, R17, R20, R23, R29. The full list includes every code from R01 to R33.