How BBSY Is Set Each Day, Who Polices It, and How to Check It Yourself

If your facility is priced at BBSY plus a margin, the base half of your interest rate is reset by the market, not by your bank. That's the main reason BBSY pricing is fairer than a bank-set reference rate. But it raises an obvious question: who actually sets BBSY each morning, what stops anyone gaming it, and how do you check the number your bank applied?

This article answers all three. If you're new to BBSY, start with BBSY Explained.

BBSY Comes From BBSW

BBSY is not calculated on its own. It's derived from BBSW, the Bank Bill Swap Rate, which is the mid-market rate for short-term bank paper. BBSY Bid is simply BBSW plus a fixed 5 basis points (0.05%). The spread is set in the benchmark rules and can't be changed without the ASX's express consent and consultation with the market.

So when people talk about how BBSY is set, they're really talking about how BBSW is set. Get BBSW right, and BBSY follows automatically.

What Determines BBSW Each Day

BBSW has been run by ASX Benchmarks, part of the ASX group, since 1 January 2017, when it took over from the Australian Financial Markets Association. It's calculated every Sydney business day for terms of one to six months.

The rate is built from real trades, not opinions:

• What's measured. Trades in bank accepted bills and negotiable certificates of deposit (NCDs) issued by the Prime Banks. Today those are the big four: ANZ, Commonwealth Bank, NAB and Westpac. Their short-term paper is the deepest, most actively traded part of the market.
• When it's measured. Only trades done in the Rate Set Window, from 8:30am to 10:00am Sydney time, count towards that day's rate.
• How it's calculated. For each term, the ASX takes the volume-weighted average yield of the eligible trades. Bigger trades carry more weight, so a single small trade can't drag the rate.
• When it's published. BBSW is published at about 10:30am Sydney time each business day. BBSY Bid and Ask are published at the same time.

Underneath all of that is the market's view of where the RBA cash rate is heading over the next few months, plus a small premium for bank credit risk. That's why 90-day BBSW usually sits a little above the cash rate, and why it can move before the RBA does. If the market expects a rate rise, 90-day BBSW starts pricing it in straight away.

The Waterfall: What Happens on a Quiet Day

Some days there isn't enough trading in a particular term to produce a reliable average. For those days, the ASX uses a fixed order of fallbacks, known as the waterfall:

• Step 1: traded prices. The volume-weighted average of eligible trades in the Rate Set Window. This is the preferred method and is used whenever there's enough volume.
• Step 2: live quotes. If there aren't enough trades, the ASX uses the best bids and offers displayed on approved trading venues during the window.
• Step 3: set fallbacks. If neither works, a series of predetermined fallback methods applies. Only at the very last stage is expert judgement from authorised staff at the Prime Banks used, and that is tightly controlled.

The order is fixed in advance and published, so nobody can choose a method on the day to get a particular result.

Why the Rules Changed: The BBSW Cases

The current system exists because the old one was exposed. Before 2018, BBSW relied much more on bank quotes in a short trading window, and thinning trade volumes made it vulnerable.

ASIC took action against four banks over their trading around the BBSW rate-setting window:

• ANZ and NAB settled in November 2017. The Federal Court found each had attempted unconscionable conduct and ordered a $10 million penalty against each, alongside enforceable undertakings to pay a further $20 million to community causes and $20 million towards ASIC's costs.
• Westpac fought the case. In May 2018 the Federal Court found it had engaged in unconscionable conduct on four days in 2010 by trading to influence where BBSW was set, though ASIC's market manipulation claims were not made out. The court ordered a $3.3 million penalty, with the judge noting he would have imposed a far higher penalty had the law then allowed it.
• Commonwealth Bank settled with ASIC and paid a $5 million penalty.

Those cases led directly to the trade-based method described above, which went live in May 2018, and to a new legal framework.

How BBSW Is Regulated Today

In 2018, Parliament added a dedicated financial benchmarks regime to the Corporations Act (Part 7.5B). Under it:

• BBSW is a "significant" benchmark. ASIC has declared BBSW a significant financial benchmark, alongside the RBA's cash rate, the S&P/ASX 200 and CPI. Significant benchmarks face the strictest rules.
• The administrator must be licensed. ASX Benchmarks has held a benchmark administrator licence from ASIC since 1 July 2019. It must follow ASIC's Financial Benchmark (Administration) Rules, covering governance, conflicts of interest, methodology, record keeping and complaints, and can be directed by ASIC.
• Banks can be compelled to take part. ASIC's Compelled Rules allow it to require banks to keep contributing to the benchmark, so the rate can't be destabilised by participants walking away.
• Manipulation is a specific crime. Manipulating a financial benchmark, or the products used to set it, is now a specific offence carrying civil and criminal penalties. Bank bills and NCDs were expressly made financial products for that purpose, closing the gap the earlier cases exposed.
• The methodology is public and tested. The ASX publishes the full BBSW conventions and methodology, an error log, a complaints policy and a regular assessment of BBSW against the international IOSCO Principles for Financial Benchmarks. Trades used in the rate are reported and checked, and unusual activity can be referred to ASIC.

The practical result for a borrower: the base rate on a BBSY facility is set by a licensed administrator, from actual trades, under rules ASIC enforces. No single bank, including yours, can move it. Your bank's discretion is confined to the margin and fees in your facility agreement.

How to Check BBSY Yourself

You don't need a trading screen to keep an eye on BBSY. A few free sources cover most needs:

• ASX BBSW 10-day history. The ASX publishes a free rolling 10-day history of BBSW mid rates for one to six months. Add 0.05% to get BBSY Bid. More detail on the methodology is on the ASX BBSW page.
• RBA statistical table F1. The RBA's daily money market table (F1), on its statistical tables page, shows end-of-day 1, 3 and 6-month bank bill rates alongside the cash rate, going back years. These are end-of-day rates rather than the 10:30am BBSW fix, so they won't match your rollover rate to the basis point, but they're ideal for tracking the trend. As at 13 October 2026, F1 showed the 3-month bank bill rate at 4.76% against a cash rate target of 4.60%.
• Market data screens. If you or your accountant have access to Bloomberg or LSEG (Refinitiv), BBSY is published in real time on those screens shortly after 10:30am.
• Your rollover notices. Each time your facility rolls, your bank should confirm the BBSY rate it applied for that rollover date and term. Keep them, and check them against the published rate for that day.

What to Check on Your Own Facility

• The date and term. Your rate should be BBSY for the term you chose (usually 30, 90 or 180 days), set on the day your rollover started.
• The right base. Confirm whether your agreement references BBSY Bid or BBSW. They differ by 0.05%, which adds up on a large facility.
• The margin. Take your all-in rate, subtract the published BBSY for your rollover date, and what's left should equal your margin and any line fee in the facility agreement. If it doesn't, ask why.
• Whether your margin is still competitive. BBSY tells you the market's half of your rate. To test the bank's half, compare your margin against the Glenclair Pricing Index, which tracks indicative margins over 90-day BBSY by asset class, gearing and lender tier.

If you want certainty over the BBSY part of your rate, see hedging BBSY for how swaps, caps and collars work, with examples from one to five years.

How We Help

We reconcile your interest charges against the published BBSY for each rollover, so you can see exactly what the market charged and what the bank charged. Where the margin is out of line, we tender your facility across our panel of 60+ lenders. Learn more about holding lenders to account, how a banking tender works and our commercial refinance service.

Book a free, no-obligation consultation and we'll check your current pricing against the market.