AT1 and CoCo Bonds: Triggers, Write-Downs, and Conversion

AT1 is a regulatory-capital category, not a single standard contract. A bank can issue an eligible instrument as a bond or another permitted form. Basel eligibility criteria require AT1 instruments to be perpetual and subordinated to depositors, general creditors, and the bank’s subordinated debt; an issuer call is not a holder right to repayment. AT1 also pays a coupon or distribution that the issuer must have full discretion to cancel. A cancellation is not necessarily a payment default. The Basel Committee’s capital definition framework sets these conditions alongside requirements for loss absorption.

“CoCo” is a market term for a security with a contingent loss-absorption feature, usually conversion into shares or a reduction of principal. Many bank AT1 bonds are CoCos, but the terms are not interchangeable: CoCos may be issued in different capital tiers, and not every AT1 instrument has identical trigger or conversion mechanics. A bond can also be written down without converting into shares. Read the issue’s legal documents instead of inferring its payoff from a product label.

AT1 is intended to provide capital while the bank is still operating as well as loss absorption in a severe failure or resolution scenario. That “going-concern” role helps explain why an AT1 trigger can occur before a formal insolvency filing. AT1 therefore differs from a conventional bond whose principal is ordinarily due at a fixed maturity and whose main credit question is whether the issuer can make scheduled payments.

Some AT1 contracts include a mechanical trigger based on a Common Equity Tier 1 (CET1) capital ratio. Under the Basel framework, liability-classified AT1 needs a principal-loss absorption mechanism at a pre-specified trigger of at least 5.125% CET1; an instrument can specify a higher threshold. The EU Capital Requirements Regulation’s Article 54 likewise sets 5.125% or a higher contractually specified level for the covered EU rule. These provisions do not mean that every AT1 in every jurisdiction has the same threshold or calculation basis.

The ratio is not a share price or a simple cash-balance measure. CET1 is defined regulatory capital divided by risk-weighted assets, and the contract and applicable rules determine the relevant issuer, group, calculation date, and treatment of the ratio. A falling ratio can bring the instrument closer to a trigger, but estimates from financial statements do not necessarily establish that the contractual event has occurred.

A separate point-of-non-viability (PONV) trigger can depend on a decision by the relevant authority. Basel’s framework describes this as the earlier of an authority deciding that write-off or conversion is necessary to prevent the bank becoming non-viable, and a decision to provide public-sector support without which the bank would become non-viable. National law may implement some powers through statute rather than repeating every power in the instrument. The trigger is qualitative and depends on the legal and supervisory framework; there is no single global numerical PONV threshold.

These mechanisms can coexist. A contract may specify both a CET1 ratio trigger and a PONV clause, with the first event under its terms activating loss absorption. It may also describe who determines the ratio, whether the trigger applies at the bank or group level, and what happens if information is delayed or disputed. The Basel Framework explains both the contractual principal-loss mechanism and the point-of-non-viability requirements; the issue documents supply the instrument-specific detail.

A write-down reduces the legal principal claim. Depending on the contract, it may be partial or complete, permanent or temporarily reversible under specified conditions. It can also reduce future coupons and the amount payable on a call or redemption. Under the Basel framework, a temporary write-down is not enough for the PONV requirement unless the terms meet the relevant loss-absorption conditions; the instrument must be capable of permanent write-off or conversion at that trigger. A holder should not assume that an amount written down will later be restored.

A conversion exchanges some or all of the AT1 claim for shares, usually common equity. The formula may set a conversion price, rate, floor, cap, or other limit. Conversion changes what the investor owns: instead of a contractual debt claim with a coupon, the holder receives equity whose value depends on the bank’s share price, dilution, rights, and prospects. The shares received may be worth far less than the principal surrendered, and the conversion can dilute existing shareholders.

The EU rule requires covered conversion terms to specify a conversion rate and limit or range, and it defines effects of a write-down on liquidation claims, redemption and distributions. The Basel standard also requires clear loss-absorption terms. Still, an EU requirement should not be presented as a universal rule for every foreign AT1. The prospectus, final terms, governing law, and incorporated definitions determine whether the outcome is a full or partial write-down, a conversion, or a sequence of actions.

The apparent puzzle is that ordinary shareholders may still hold shares when an AT1 contract absorbs losses. This can happen because AT1 is designed to operate as going-concern capital: a ratio trigger or a PONV event can activate before the bank has entered a court insolvency process. Whether that is permitted, what it does to principal, and whether equity must be reduced first depend on the contract and the jurisdiction’s rules.

It helps to distinguish two different orderings. Payment or creditor ranking describes who has a claim ahead of whom when assets are distributed in liquidation. Loss-absorption or resolution sequence describes how a regulator can reduce or convert capital instruments when a bank is failing. The Bank of England’s statement on the UK hierarchy says AT1 ranks ahead of CET1 shareholders and behind Tier 2 claims in that creditor hierarchy. Separately, the European Banking Authority’s guidance on the EU sequence explains that CET1 capacity is reduced before AT1, followed by Tier 2, when the relevant resolution powers are used. These statements address related but distinct legal questions; neither establishes a universal ranking for every country or issue.

The governing law, resolution framework, contract trigger, issuer structure, and any statutory write-down power all matter. A prospectus may explain how a particular AT1 interacts with equity or other capital, but the prospectus cannot be read without the laws that govern resolution. Use the instrument’s ranking language and the competent authority’s current rules rather than applying a headline such as “equity always goes first” or “AT1 is always written off first.”

In March 2023, FINMA directed Credit Suisse to write down all of its AT1 instruments, with about CHF 16.5 billion in nominal principal affected. FINMA said the instruments’ prospectuses made a full write-down available following a “Viability Event,” particularly extraordinary government support, and that the emergency liquidity assistance backed by a federal guarantee met those contractual conditions. The authority also relied on the Swiss Federal Council’s emergency ordinance. This is FINMA’s account of the action, not a template for interpreting another issuer’s AT1.

The legal status later changed. On 1 October 2025, the Swiss Federal Administrative Court issued a partial decision in one proceeding, finding that FINMA’s order lacked a legal basis and revoking that decree. The court did not decide the request to reverse the write-down. In a separate notice, FINMA said it would appeal to the Federal Supreme Court, and the administrative court said in its October 2025 suspension notice that the other pending cases were stayed while the leading case proceeded. The cited official notices describe the decision as non-final and do not establish the final outcome or any restitution. Readers should check the Swiss authorities’ later docket updates before relying on this procedural snapshot.

The case is useful because it separates several questions that are often collapsed: what the note prospectus said, whether its contractual trigger was met, what statutory powers applied, and whether the regulator’s order had a sufficient legal basis. It does not prove that all AT1 holders rank behind shareholders in every jurisdiction, nor does it establish that every government liquidity measure triggers every AT1. Different issuers can have different Viability Event definitions, capital ratios, statutory frameworks, and resolution sequences.

The court’s partial-decision notice records that ruling and the unresolved request for reversal.

Suppose, only for illustration, an investor buys $10,000 face amount of an AT1 note whose hypothetical terms provide for a permanent full write-down if a specified trigger is reached. Assume the contract’s defined CET1 measure crosses its stated threshold and the required authority action occurs. Under those assumptions, the investor could lose the full $10,000 principal claim; the contract may also end or reduce future distributions. This is not a prediction about any bank or a description of a live security. Another instrument might provide for a partial write-down or conversion instead.

If a hypothetical note converted into shares, the investor would receive the number and class of shares determined by the contract—not a promise to recover the original $10,000. Their market value could be higher or lower, and dilution or trading restrictions may matter. Even before a trigger, AT1 prices can move sharply as markets reassess a bank’s capital, liquidity, earnings, or political and legal environment. Coupons can be cancelled, maturity can be perpetual or extended, and a holder may have difficulty selling during stress.

Other risks include uncertainty about when a trigger is measured, the issuer or group to which the ratio applies, regulator discretion under PONV provisions, conversion valuation, call expectations, changing benchmark rates, market liquidity, and cross-border enforcement. A high coupon does not compensate automatically for these risks. The hypothetical example illustrates how principal exposure works; it is not a yield forecast or an investment recommendation.

Start with the exact issuer and capital instrument: bank subsidiary or holding company, currency, governing law, issue date, and whether it is legally debt or another form. Find the stated CET1 trigger and its calculation perimeter, then read the PONV or “Viability Event” definition, who determines it, and whether a public-support event is included. Note if the terms refer to the solo bank, a consolidated group, or another entity.

Next, identify the result when a trigger occurs. Is principal written down fully or partially? Is the write-down permanent, or is any write-up permitted under a defined mechanism? If conversion is possible, what shares are issued, at what price or formula, and with what cap, floor, dilution, or shareholder rights? Check whether coupons may be cancelled at the bank’s discretion, whether cancelled amounts accumulate, whether cancellation is a default, and how the instrument ranks for liquidation and resolution purposes.

Finally, check call and extension language, redemption conditions, tax and currency provisions, listing and transfer limits, and the risk factors in the full prospectus—not only the marketing summary. Compare the documents with the issuer’s current capital disclosures and the applicable regulator’s rules. For related background, see secured and unsecured bond ranking, bond covenants and indentures, and how corporate bond ratings change. This guide explains general mechanics, not the legal effect of a particular instrument or a recommendation to buy or sell one.

Treat the prospectus, the law governing the issuer, and the applicable resolution framework as one set of documents. A headline about a trigger or payment rank cannot answer all three questions: what event activates loss absorption, what happens to the investor’s claim, and how that claim ranks if the bank enters resolution or liquidation. Check those terms together and date any legal-status summary.