What Is the Bank Bill Swap Bid Rate (BBSY)?

What Is the Bank Bill Swap Bid Rate (BBSY)?

3 Min.

BBSY, or Bank Bill Swap Bid Rate, is a type of short-term floating interest rate used by banks, financial institutions, and investors worldwide. Though its name may differ, it is often known as "swap rates." Even small changes in the rate can have significant consequences.


Originating from Australia, the Bank Bill Swap Bid Rate (BBSY) stands as a pivotal benchmark interest rate. This significant metric finds its dissemination through Thompson Reuters Information Service, a prominent data provider. The BBSY garners frequent utilization among financial institutions and corporations partaking in activities involving interest rate swaps and interconnected transactions.

Deciphering BBSY in the Australian Context 

In Australia, BBSY plays a pivotal role as the interest rate shaping financial market dynamics. It underpins the pricing and assessment of Australian dollar securities and forms the bedrock for bank borrowings and short-term floating interest rates. Responsible for its management is ASX Ltd, the entity steering Australia's primary national stock exchange and equity derivatives market.

BBSY finds its daily unveiling at 10:15 a.m. on Thomson Reuters and Bloomberg LLP. These disclosed rates serve as the cornerstone for national financial institutions in computing interest rates on financial agreements. This transparent mechanism bolsters efficiency within the nation's financial framework.

Functioning as the cornerstone for debt financing, BBSY mirrors the renowned London Interbank Offer Rate (LIBOR). Its derivation rests upon the Bank Bill Swap Rate (BBSW) computed as the average of the national best bid and best offer (NBBO), rounded to four decimal places.

This mean mid-price is furnished by impartial authorities utilizing a lucid algorithm built upon inputs from multiple financial institutions. Parallel to this process, BBSY is computed and dispensed, albeit employing the average bid price instead of the mid-price.

BBSY Application Example

An illustrative scenario involving the bank bill swap bid rate demonstrates its utility in a straightforward interest rate swap arrangement. This financial agreement pairs two parties, jointly electing to exchange interest payment flows for a predefined term. One participant exchanges fixed-interest disbursements for fluctuating interest receipts intricately tied to the fluctuations of the BBSY.

The determination of the interest rate dictating payment sums hinges on the inception stage of the pact, with the BBSY chosen as the pivotal benchmark. The floating rate integrated into interest rate swaps constitutes BBSY supplemented by (or diminished by) a margin (e.g., BBSY + 35 basis points).

Imagine two enterprises engaging in an interest rate swap: company XYZ is making fixed payments to and gaining variable payments from company ABC. With a semi-annual fixed interest rate at 2% and the floating rate set at BBSY + 0.35%, payments are exchanged over a notional principal sum of $1 million. On the computation day, XYZ disburses 1/2 * 0.02 (interest rate 2%) * $1 million = $10,000 to ABC. Assuming the BBSY stands at 1.90%, ABC remits 1/2 * 0.0225 (1.90% + 0.35%) * $1 million = $11,250 to XYZ.


The Bank Bill Swap Bid Rate is a crucial tool in global finance. Known as "swap rates," it impacts institutions worldwide, with even slight changes carrying significant weight. In Australia, BBSY shapes rates alongside ASX Ltd., while its daily disclosure on platforms like Thomson Reuters and Bloomberg bolsters transparency and efficiency. In debt financing, it mirrors the London Interbank Offer Rate (LIBOR). BBSY guides interest rate swaps, orchestrating payments and demonstrating its dynamic role in financial exchanges and modern finance.

Bank Bill Swap Bid Rate (BBSY)
London Interbank Offer Rate (LIBOR)
Bank Bill Swap Rate (BBSW)
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