Routing Number

What routing numbers do

A nine-digit code that:

• Identifies a specific US bank or credit union.
• Used for ACH, wire, and check processing.
• Combined with account number to fully address a transaction.
• Different routing numbers for different transaction types at the same bank.

The number directs financial transactions to the right institution.

Where to find it

Several locations:

• Bottom of paper checks — leftmost nine digits.
• Online banking — typically displayed in account information.
• Bank's website — usually published.
• Direct deposit forms from employer.

Different routing numbers may apply to different uses (ACH vs. wire vs. domestic vs. international).

How it's structured

The nine digits encode:

• First four digits — Federal Reserve routing symbol.
• Next four digits — institution identifier.
• Last digit — checksum.

The structure dates to 1910 paper-check processing era; still used because of installed-base effects.

Routing for different transactions

Different needs:

• ACH transfers — typically uses standard routing number.
• Wire transfers — sometimes a different routing number.
• International wires — uses SWIFT codes rather than routing numbers.
• Direct deposit — same as ACH.

For domestic transactions within the US, routing number plus account number is usually sufficient.

Common pitfalls

A few patterns:

• Wrong routing number — transaction may bounce or go to wrong institution.
• Mixing wire vs. ACH routing numbers.
• Outdated routing numbers after bank mergers — new institution may have different numbers.
• Verification — always double-check before sending large amounts.

What individuals should know

For most banking activity:

• Routing number is part of standard transactions.
• Most apps autopopulate when account is linked.
• Verify before manual entry for important transactions.
• Different routing numbers can apply to different transaction types.

The routing number is one of crypto's predecessors — a system for directing financial value across institutions. The crypto equivalent is wallet addresses, which serve a similar purpose without requiring the institutional middleman.

For most users, routing numbers are background infrastructure that just works. The exception is when manual entry is required — verification matters.