An Additional Tier 1 bond, usually called an AT1 bond, is a perpetual, subordinated bond issued by a bank that is contractually designed to absorb losses while the bank is still operating. In return for high yields, the investor accepts that the bank can cancel coupons at will, may never redeem the principal, and can have the bond written down to zero or converted into shares if the bank’s capital falls too low. Roughly CHF 16 billion of these instruments were wiped out overnight when Credit Suisse failed in March 2023, which is the clearest illustration of what the instrument is actually for.1IISD. Switzerland Faces ISDS Claims Over Credit Suisse AT1 Bond Write-Off
Where AT1 Sits in a Bank’s Capital Structure
AT1 bonds exist because of the Basel III reforms adopted in 2010 after the 2008 financial crisis. Regulators wanted banks to hold more loss-absorbing capital and wanted private investors, not taxpayers, to take the hit when a bank got into trouble.2Bank for International Settlements. Definition of Capital in Basel III
Under Basel III, the strongest layer of bank capital is Common Equity Tier 1 (CET1), made up of common stock and retained earnings. Additional Tier 1 sits directly beneath that, filled primarily by AT1 bonds. Together, CET1 and AT1 make up Tier 1, or “going concern,” capital, meaning it can absorb losses while the bank is still running. Tier 2 capital only absorbs losses in liquidation.2Bank for International Settlements. Definition of Capital in Basel III
That ordering is the point. If a bank’s finances deteriorate, AT1 holders are meant to lose money before Tier 2 or senior creditors are touched.3Suara SEACEN. Loss Absorbency of Additional Tier 1 Capital Instruments under Basel III: The Credit Suisse Case
How an AT1 Bond Actually Behaves
It Has No Maturity Date
AT1 bonds are perpetual. That is what makes them eligible as Tier 1 capital in the first place; instruments with a fixed maturity can only qualify as Tier 2.2Bank for International Settlements. Definition of Capital in Basel III There is no repayment date the investor can rely on.
The Bank May Call It, or Not
Most AT1 bonds include an issuer call, usually exercisable after five or ten years. Basel III requires at least five years before the first call and prohibits step-up coupons or other features that would create an expectation of redemption.4Bank for International Settlements. Basel III Definition of Capital – Frequently Asked Questions
A call is never automatic. The bank needs supervisory approval, which is generally granted only if the called bond is replaced with capital of equal or better quality, or the bank’s capital position remains well above minimums.4Bank for International Settlements. Basel III Definition of Capital – Frequently Asked Questions European regulators have said banks should not announce a call before receiving approval.5European Banking Authority. Continuous Call Option in AT1 Instruments
If the bank chooses not to call, the coupon resets to a fixed credit spread set at issuance plus a current benchmark swap rate. Because step-ups are not allowed, the new rate can be lower than the original. The bond then continues indefinitely, and its market price typically drops sharply. This is called extension risk.
Coupons Are Discretionary and Non-Cumulative
The bank can cancel any scheduled coupon at any time, for any reason. Skipping a coupon is not a default, and the missed payment is gone forever; the bank owes nothing later.6Bank for International Settlements. Basel III: A Global Regulatory Framework for More Resilient Banks and Banking Systems
Cancellation becomes most likely when the bank’s CET1 ratio slips into the capital conservation buffer above the minimums, at which point regulators progressively restrict dividends, buybacks, and discretionary payments.7Bank for International Settlements. RBC30 – Buffers Above the Regulatory Minimum The market calls this the Maximum Distributable Amount constraint, and it directly threatens AT1 coupon payments. But contractually, the bank does not need any regulatory reason to cancel. Coupon income can disappear permanently while the principal remains outstanding.
The Core Risk: Loss Absorption
An AT1 bondholder’s principal can be destroyed. That is not fine print. It is the reason the instrument qualifies as regulatory capital.
The CET1 Trigger
Every AT1 bond has a contractual trigger tied to the issuing bank’s CET1 ratio. Basel sets the floor at 5.125% of risk-weighted assets for instruments classified as liabilities, and some regulators require higher.8Bank for International Settlements. FSI Briefs No 21 – Upside Down: When AT1 Instruments Absorb Losses Before Equity The Bank of England, for instance, sets the trigger at 7%, and many European issuers use that level voluntarily.9The Banker. How AT1 Bonds Have Made a Comeback
Once the trigger is breached, the bond’s terms mandate one of two outcomes, fixed at issuance:
- A principal write-down, which reduces the bond’s face value partially or fully. Depending on jurisdiction, this can be temporary with a possible write-back if the bank returns to profit, or permanent.8Bank for International Settlements. FSI Briefs No 21 – Upside Down: When AT1 Instruments Absorb Losses Before Equity
- A mandatory conversion into common shares at a pre-set ratio. Because conversion happens during distress, the shares are usually worth far less than the bond’s face value.
Either action lifts the bank’s CET1 ratio. Neither is subject to the bank’s discretion once triggered, and neither is subject to the investor’s consent.
The Point of Non-Viability Trigger
Separately, regulators can impose losses on AT1 holders when they judge the bank has reached the point of non-viability. Basel defines that as the earlier of the authority deciding a write-down is needed to restore viability, or a decision to provide public support to keep the bank alive.8Bank for International Settlements. FSI Briefs No 21 – Upside Down: When AT1 Instruments Absorb Losses Before Equity
This trigger can be pulled even if the CET1 threshold has not been breached. The idea is that private capital gets wiped out before any public money goes in.
What Credit Suisse Showed
In March 2023, Swiss regulator FINMA ordered the full write-down of about CHF 16 billion in Credit Suisse AT1 bonds as part of the emergency takeover by UBS.1IISD. Switzerland Faces ISDS Claims Over Credit Suisse AT1 Bond Write-Off The authority came from a Federal Council emergency ordinance.10Finadium. FINMA to Appeal Swiss Court Ruling That CS AT1 Write-Downs Lacked Legal Basis
What made the decision explosive was that Credit Suisse shareholders received compensation through the UBS share exchange while AT1 holders received nothing. In the ordinary creditor hierarchy, equity is wiped out before subordinated debt. The Swiss outcome inverted that order. European regulators promptly issued statements reaffirming that in their jurisdictions, equity would absorb losses before AT1 instruments.
A Swiss court later ruled the write-down lacked a sufficient legal basis; FINMA appealed. For any prospective AT1 investor, the episode is the clearest available lesson: the write-down risk is real, regulatory discretion can override expected creditor hierarchies, and the legal framework varies by jurisdiction in ways that matter.
Yield and the Risks Priced Into It
AT1 bonds sit in the high-yield corner of fixed income. The elevated coupons compensate investors for subordination, perpetual duration, discretionary payments, and the possibility of losing everything. The most commonly cited yield metric is yield-to-call, which assumes the bank redeems at the first call date.
The global AT1 market totals roughly $280 billion outstanding. European AT1 spreads had tightened to around 390 basis points over benchmarks by early 2024, below the long-term average of about 450 basis points, and compressed further toward all-time tights by early 2026. Investor appetite recovered quickly after the Credit Suisse shock, which suggests institutional buyers treated the write-down as a jurisdiction-specific outcome rather than a structural flaw.
Three specific risks show up in the pricing. Extension risk is the possibility the bank does not call at the first opportunity, in which case the coupon resets and the market price typically falls; historically most large banks have called to preserve access to future issuance, but there is no guarantee. Coupon cancellation risk widens spreads whenever a bank’s CET1 ratio drifts toward the buffer zone. Regulatory risk is harder to model because it depends on policy decisions rather than financial metrics, and, as Credit Suisse demonstrated, an emergency ordinance can expand regulatory powers beyond what the bond prospectus anticipated.
Who Can Actually Buy Them
In the United States, AT1 bonds are typically offered as private placements under SEC Rule 144A. They are not registered with the SEC and are not sold to the general public. A buyer generally must qualify as a “qualified institutional buyer,” which usually means owning and investing on a discretionary basis at least $100 million in securities of unaffiliated issuers. Registered broker-dealers face a $10 million threshold.11eCFR. 17 CFR 230.144A – Private Resales of Securities to Institutions
Even where retail access is technically permitted, the instrument’s complexity puts it out of reach for most individuals. Perpetual duration, discretionary coupons, and the real prospect of a full write-down require credit analysis and regulatory-capital modeling most retail investors are not equipped to perform. The buyer base is dominated by asset managers, insurance companies, pension funds, and hedge funds with dedicated bank capital desks.