BSB

A Bank State Branch number, almost always abbreviated BSB, is a unique six-digit code that identifies an individual branch of an Australian bank or credit union. Every branch has its own BSB, and the code is used together with the customer's account number to identify precisely where a payment should be routed, functioning similarly to a routing number in the United States or a sort code in the United Kingdom and Ireland.

Despite the name referencing a physical branch, BSB numbers continue to be used for electronic and direct-entry payments in Australia even as branch banking itself has declined, because the numbering system remains embedded in the core infrastructure banks use to clear and settle domestic payments.

A BSB is simply the postcode of Australian banking: a short code telling the system exactly which institution, and historically which branch, an account belongs to, so a payment ends up in the right place.

• The first two digits typically identify the bank or financial institution.
• The remaining digits historically identified the specific branch, though many banks now map multiple logical BSBs to centralized processing rather than a physical location.
• The BSB is always paired with an account number when giving payment details to a third party.

Even as physical branches close across Australia, the BSB numbering system remains the backbone of how domestic payments are routed and reconciled, meaning customers will likely continue quoting a BSB long after the specific branch it originally referred to has ceased to exist as a physical location.

Newer Australian payment systems, such as the PayID service built on the New Payments Platform, let customers receive payments using a phone number or email address instead of quoting a BSB and account number, though the underlying BSB and account number still exist behind the scenes for the actual settlement.

Because a BSB and account number together determine where a payment lands, a single-digit error when quoting a BSB can misroute a payment to an entirely different bank, which is why many payment systems now include validation checks before a transfer is finalised to catch obviously invalid BSB and account number combinations.

A new bank or credit union entering the Australian market must be allocated one or more BSB numbers before it can participate in domestic payment clearing, a formal registration step administered centrally to ensure no two institutions are ever assigned the same identifying code.

When banks merge or consolidate branches, old BSB numbers are often retained for compatibility even after the physical branch they originally represented has closed, which is why some BSB numbers in circulation today no longer correspond to any operating physical location.

Unlike some mobile phone numbers that customers can port between providers, a BSB and account number combination cannot be transferred if a customer switches banks, meaning anyone changing banks needs to update their BSB and account details with every employer, biller and counterparty who previously had the old payment details on file.

Australia's New Payments Platform was built to coexist with, rather than replace, the BSB and account number system, meaning most newer real-time payment features still ultimately rely on the same underlying BSB-based routing to actually move money between institutions, even when the customer-facing experience relies on a simpler identifier such as a phone number.

Business customers managing payments across multiple bank accounts sometimes maintain an internal reference sheet mapping each BSB and account number to its purpose, a simple but practical control that reduces the risk of a payment being sent to the wrong internal account purely through a data-entry mistake.

Financial literacy resources aimed at new bank customers in Australia typically explain the BSB early on, since misunderstanding its purpose is a common source of confusion for people more familiar with a single all-in-one account number used in other countries.