How Bank Mergers Affect BSB Numbers

Why Bank Mergers Matter for BSB Numbers

Australia's banking landscape has changed significantly over the past few decades, with a series of mergers and acquisitions reshaping the industry. When two financial institutions merge, one of the many practical details that must be resolved is what happens to the BSB numbers held by the acquired bank's customers.

BSB numbers are deeply embedded in Australia's payments infrastructure. They are stored in payroll systems, direct debit arrangements, government payment records, and personal banking details shared between individuals. A poorly managed BSB transition during a merger can cause missed salary payments, failed bill payments, and widespread confusion for customers.

Understanding how mergers affect BSB numbers helps customers prepare for changes and avoid disruptions to their banking.

What Happens to BSB Numbers During a Merger

When one bank acquires another, the acquired bank's BSB numbers do not simply vanish overnight. The transition typically follows a structured process:

Phase 1: Announcement and Continuation

When a merger is first announced and completed, the acquired bank's BSB numbers continue to function as normal. Payments routed to the old BSB numbers are processed without interruption. Customers are not required to take any immediate action.

During this phase, the acquiring bank is working behind the scenes to integrate the two institutions' systems, accounts, and branch networks. This technical integration can take months or even years.

Phase 2: Migration and Dual Operation

As integration progresses, the acquiring bank may begin migrating customers to new BSB numbers that align with its own numbering system. During this phase, both the old and new BSB numbers are active. Payments sent to either number are successfully routed.

This dual-operation period is critical for minimising disruption. It gives customers, employers, billers, and government agencies time to update their records with the new BSB details.

Phase 3: Redirection

After a sufficient transition period, the acquired bank's original BSB numbers may be formally decommissioned. However, in practice, many acquiring banks maintain automatic redirections from old BSB numbers to new ones for extended periods -- sometimes years. These redirections ensure that payments sent to outdated BSB numbers are still delivered to the correct account.

Phase 4: Final Decommissioning

Eventually, the old BSB numbers may be fully retired. At this point, payments sent to the decommissioned BSB will fail. However, most banks ensure that this final stage occurs only after an extensive transition period and significant customer communication.

Notable Australian Bank Mergers and Their BSB Impact

St George Bank and Westpac (2008)

One of the most significant mergers in recent Australian banking history was Westpac's acquisition of St George Bank in 2008. St George had a substantial customer base across New South Wales and other states, with BSB numbers in the 11x and 33x ranges.

After the merger, Westpac chose to maintain St George as a separate brand. St George branches continued to operate under the St George name, and the existing St George BSB numbers remained active. Customers were not migrated to Westpac BSB numbers (03x range).

This brand-preservation approach meant that BSB disruption was minimal. St George customers retained their existing BSB numbers, and the 11x prefix continues to be associated with St George to this day. The same approach was applied to BankSA (10x) and Bank of Melbourne (19x), which also operate as separate brands under the Westpac Group.

BankWest and Commonwealth Bank (2008)

In the same year, Commonwealth Bank acquired BankWest from its parent company HBOS during the global financial crisis. BankWest, which was particularly strong in Western Australia, used BSB numbers in the 30x range.

Similar to the St George situation, CBA opted to retain BankWest as a distinct brand. BankWest BSB numbers in the 30x range were preserved, and customers were not required to switch to CBA's 06x BSB range. BankWest continues to operate with its own BSB numbers under Commonwealth Bank's ownership.

Bendigo Bank and Adelaide Bank (2007)

The merger of Bendigo Bank and Adelaide Bank in 2007 created Bendigo and Adelaide Bank, one of Australia's largest regional banks. Bendigo Bank used BSB numbers in the 63x range, while Adelaide Bank used the 61x range.

Post-merger, both BSB ranges were maintained. Customers of each legacy institution retained their existing BSB numbers. The merged entity continues to operate branches and accounts under both BSB ranges.

Suncorp and Metway (1996) and Subsequent Acquisitions

Suncorp's merger with Metway Bank in 1996 (forming Suncorp-Metway, later simply Suncorp) involved the consolidation of BSB numbers over time. Suncorp Bank currently uses the 48x and 64x ranges, reflecting its history of mergers and integrations.

Credit Union Consolidations

The credit union and mutual banking sector has seen extensive consolidation over the past two decades, with hundreds of small institutions merging into larger entities. These mergers often involve migrating customers from one BSB range to another, particularly when the smaller institution operated under a shared clearing arrangement through Cuscal (80x range).

In many credit union mergers, the larger institution absorbs the smaller one's members and transitions them to new BSB numbers. Because credit unions typically have fewer commercial and payroll relationships than major banks, these transitions tend to be less disruptive, though they still require careful customer communication.

What Customers Should Do During a Bank Merger

If your bank is involved in a merger or acquisition, here are the steps you should take to ensure your banking is not disrupted:

1. Watch for Communications from Your Bank

Your bank is required to notify you of any changes to your BSB number. Watch for letters, emails, in-app notifications, and SMS messages from your bank. These communications will explain the timeline, your new BSB (if applicable), and what action you need to take.

2. Update Your Employer

If your BSB number changes, notify your employer or payroll department so they can update their records. This is particularly important for salary payments, as a failed payment can delay your income. Do not wait until the last minute -- update your payroll details as soon as your new BSB is confirmed.

3. Update Direct Debits and Billers

Review all direct debit arrangements linked to your account. Contact each biller -- utility companies, insurance providers, subscription services, loan providers -- and provide your updated BSB number. Many billers allow you to update payment details through their website or app.

4. Notify Government Agencies

If you receive payments from government agencies such as the Australian Taxation Office (ATO), Services Australia (Centrelink, Medicare), or the Department of Veterans' Affairs, update your bank details with these organisations. Government systems may not automatically pick up BSB redirections, and outdated details can delay benefit payments or tax refunds.

5. Inform Anyone Who Transfers Money to You

If friends or family regularly transfer money to you, let them know your new BSB number. While redirections will likely catch most payments during the transition period, it is better to be proactive than to rely on temporary routing arrangements.

6. Update Stored Payment Details

Check any platforms or services where you have stored your bank account details for payouts, such as freelancing platforms, marketplace sellers (eBay, Amazon), share registries, or superannuation funds. Update your BSB number in each of these systems.

7. Verify with BSBFinder

After a merger, use BSBFinder to verify that your new BSB number is active and correctly associated with your bank and branch. This simple check can provide peace of mind that your updated details are correct before you begin using them.

How Long Do Transition Periods Last?

There is no fixed rule for how long a BSB transition period lasts. It depends on the complexity of the merger, the number of affected customers, and the acquiring bank's integration strategy. In general:

• Brand-preserving mergers (e.g., St George under Westpac, BankWest under CBA) may result in no BSB change at all. The acquired brand's BSB numbers continue indefinitely.
• Full integration mergers typically provide at least 12 to 18 months of dual BSB operation, during which both old and new BSB numbers work.
• BSB redirections after decommissioning the old numbers can last several years, providing an additional safety net for late-updating customers.

The industry body that manages the BSB directory coordinates these transitions and publishes regular updates so that all participating institutions have current routing information.

Will Your Account Number Change Too?

In many mergers, your account number remains the same even if your BSB changes. However, this is not guaranteed. Some integrations require both the BSB and account number to change, particularly if the two institutions' account numbering systems are incompatible.

Your bank will clearly communicate if your account number is changing in addition to your BSB. If both change, treat the transition with extra care and update all relevant parties with both pieces of new information.

Staying Informed

Bank mergers are a normal part of the financial industry, and Australian regulators and industry bodies have well-established processes for managing BSB transitions. The best thing you can do as a customer is stay informed, act on communications from your bank, and proactively update your details with employers, billers, and anyone else who sends you money. If you are ever unsure whether a BSB number is current, a quick lookup on BSBFinder will give you the answer.