The Betashares Australian Major Bank Subordinated Debt ETF (ASX: BSUB) offers Australians targeted access to a specific corner of the fixed-income market: the subordinated bonds issued by the four major Australian banks. As bank hybrids are phased out, subordinated debt from the big four has drawn attention as an income alternative with a defensive, floating-rate character.

In September 2026, with the Reserve Bank holding its cash rate at 4.35% and income investors weighing their options, BSUB sits in an increasingly relevant part of the market. This article explains how BSUB works, why it is in focus, and the catalysts and risks that could shape it from here.

What is the BSUB ETF?

BSUB is a passive fixed-income ETF issued by Betashares. It aims to track, before fees and expenses, an index of floating-rate Tier-2 subordinated bonds issued by the four major Australian banks — Commonwealth Bank, Westpac, ANZ and NAB. Eligible bonds must have at least $500 million outstanding and a remaining maximum term to Maturity of ten years, and the fund can hold a maximum of 16 securities, with an issuer cap of around 35% when there are enough bonds. The fund charges management costs of around 0.29% per annum and pays income.

The defining feature is its exclusive focus on big-four bank subordinated debt. Subordinated (Tier-2) bonds rank behind senior bonds but ahead of hybrids and Equity in a bank’s capital structure, so they offer a Yield premium over senior bank bonds to compensate for that additional risk. Because the bonds are floating-rate, BSUB has low interest-rate (duration) risk — its capital value is relatively stable, trading around A$25, and its income moves with short-term rates. Its concentration in the big four, which are among the best-capitalised banks in the world, is central to its risk profile.

What is driving interest now?

A major driver is the structural change in the Australian income market. Regulators have set in motion the phase-out of bank hybrid securities, a long-standing source of income for many Australian investors. As hybrids are wound down, investors are looking for alternatives, and subordinated debt from the major banks — a related but higher-ranking part of the bank Capital Structure — has emerged as one option. BSUB offers focused access to that market.

The second driver is the yield on offer. With the RBA holding at 4.35% and cash and bond yields elevated, income-seeking investors are weighing their options. Subordinated debt offers a yield premium over senior bank bonds and cash, in exchange for taking subordinated Credit risk, while its floating-rate structure means its income moves with rates and its capital value stays relatively stable. That combination — attractive income, low duration, and exposure to the well-capitalised major banks — has made it an income story worth watching.

Portfolio and holdings

BSUB’s portfolio is a concentrated group of floating-rate subordinated bonds, holding a maximum of 16 securities, all issued by the four major Australian banks. That exclusive focus on the big four is the defining feature: the fund’s performance and income depend entirely on the creditworthiness of Commonwealth Bank, Westpac, ANZ and NAB, and on the pricing of their subordinated debt.

Two features define BSUB’s behaviour. First, because the bonds are floating-rate, the fund has low duration, so its unit price is relatively stable and its income moves with short-term rates. Second, its main risk is credit-related and highly concentrated in the big four banks — though these are among the best-capitalised financial institutions in the world. Investors should understand that BSUB is a focused, income-oriented holding whose fortunes depend on the major banks and on the subordinated-debt market, sitting a step higher in the capital structure than hybrids but below senior bonds.

Catalysts to watch

Several factors could influence BSUB in the coming months: the ongoing phase-out of bank hybrids and how investors reallocate that income; the RBA’s rate path and the level of floating-rate yields; the creditworthiness and funding conditions of the major banks; credit spreads on subordinated debt; and new issuance in the big-four subordinated-bond market.

Risks

BSUB carries risks specific to bank subordinated debt. Credit risk is central, and highly concentrated in the four major banks. Subordinated ranking risk means the bonds rank behind senior debt, so holders face greater loss if a bank fails. Concentration risk is significant given the exclusive big-four focus and the small number of holdings. Interest-rate risk is low given the floating-rate structure, but income falls if rates decline. Liquidity Risk can arise in stressed markets. Regulatory change affecting bank capital instruments is an ongoing consideration. Market Risk applies.

Outlook

BSUB offers Australians focused access to big-four bank subordinated debt, an income option that has grown in relevance as bank hybrids are phased out. Its near-term appeal rests on the yield available from subordinated debt relative to cash and senior bonds, and on the continued strength of the major banks. Investors may be watching the hybrid phase-out, the RBA’s rate path and bank credit conditions for direction. The outlook may depend on how the income landscape evolves as hybrids wind down and on the health of Australia’s major banks, which underpin the entire fund.