Entering an incorrect nine-digit routing number when setting up a direct deposit, electronic bill payment, or Automated Clearing House transfer typically results in the transaction being rejected or delayed by the financial institutions involved. Because routing numbers identify specific banks or regional processing centers, an invalid number will fail validation checks, causing the funds to bounce back to the originating account within a few business days. If the incorrect routing number happens to match a completely different real bank, the transaction may be misrouted to that institution, where internal account verification checks will usually catch the mismatch and reject the deposit, though resolving the resulting tracking delay requires contacting customer support.