Basel III and bank crisis rules: the leverage limits after 2008

What is Basel III in plain English?

The Basel Committee on Banking Supervision published the Basel III standards in September 2010, and central banks began implementing them shortly after (Wikipedia, Basel III). In plain English, the standards tell banks how much loss-absorbing capital to hold, how far to borrow against it, and how many cash-like assets to keep for a run. A standard becomes binding only when a country adopts it, so the same ratio can start on different dates in different places.

The rules answer 3 weak points of 2008: thin capital, heavy borrowing, and fragile funding. Each weak point gets its own ratio, and the ratios work together. A bank can meet one and fail another, so the supervisor reads the full set and not a single number.

Which capital ratios does Basel III require?

Basel III requires a minimum common equity tier 1 ratio of 4.5% of risk-weighted assets, a Tier 1 minimum of 6% at all times, and total capital above 8% (Wikipedia, Basel III). Common equity is the strongest layer, since it absorbs losses first. Tier 1 and Tier 2 add further layers behind it. Risk-weighted assets scale each asset by its risk, so a safe government bond needs less capital behind it than a risky loan.

On top of the minimums sits a capital conservation buffer equivalent to at least 2.5% of risk-weighted assets, and national regulators may add a countercyclical buffer of up to 2.5% in common equity. Buffers work like a safety margin: a bank can draw on them in stress and then rebuild them in calmer years.

How does the Basel III leverage ratio limit bank borrowing?

Basel III introduced a minimum leverage ratio of 3% (Wikipedia, Basel III). A 3% ratio equals about 33 times capital in exposure, because 100 divided by 3 is about 33. The ratio applies the same weight to every exposure, so it gives a backstop when risk weights understate the danger.

National rules can go higher. The United States applies a supplementary leverage ratio above 3.0%, with a 5% minimum for large banks and systemically important institutions, and the UK sets 3.25% for banks with deposits over £50 billion. The finalisation reforms also add a leverage ratio buffer for G-SIBs, set at 50% of a G-SIB’s risk-weighted capital buffer.

How do Basel III liquidity rules protect banks in a run?

The liquidity coverage ratio requires high-quality liquid assets to cover net cash outflows over 30 days under stress, at least 100% (Wikipedia, Basel III). It targets the 2008 pattern in which funding dried up quickly and banks had to sell assets while prices were falling. A ratio of 100% means that liquid assets match the expected outflows over the 30 days.

The net stable funding ratio looks at a horizon of 1 year: available stable funding must exceed required stable funding, a ratio above 100%. Together the 2 liquidity ratios cover a month of stress and a year of structure. Capital absorbs losses, and liquidity buys time to absorb them.

What extra capital do systemically important banks hold under Basel III?

In November 2010 the Basel Committee introduced capital surcharges for global systemically important banks, and the G-SIB surcharge framework was finalised in 2011 (Wikipedia, Systemically important financial institution). The United States requires an additional 1% of common equity for G-SIBs (Wikipedia, Basel III). The surcharge prices the risk that a failure would reach beyond the bank.

The Financial Stability Board’s November 2025 update listed 29 global systemically important banks. A surcharge links the too big to fail debate to a number: the larger and more interconnected the firm, the more loss-absorbing capital it holds. Banks on the list face the surcharge and the leverage buffer together.

Where does Basel III implementation stand across countries?

Implementation runs on national timetables. The revised securitisation framework took effect in 2018 and the standards for interest rate risk in the banking book in 2023. Canada implemented in the early 2020s, and Japan phases in Basel 3.1 from 2024 to 2029 (Wikipedia, Basel III).

The EU schedules completion in 2027 with a 3-year phase-in, the UK Standardised Approach begins on 1 January 2027 and its Internal Models Approach on 1 January 2028, and India implements in April 2027. The United States rewrote a 2023 proposal in 2026, and its timeline is uncertain. Check the local date before applying a ratio.

How can Basel III ratios guide bank crisis risk work today?

Basel III turns the 2008 lessons into 3 questions for any bank: how much capital sits behind its risk, how much it borrows against that capital, and how much liquid cash it can raise in a run. As of October 2026, those questions apply to a counterparty, a lender, or a bank that holds your deposits. This page is general information, not investment advice.

Ratios describe a bank on a reporting date. A structural score adds the system view: how stability, transparency, and trust interact across banks. The EQOS Asia method page explains the approach, and the simulator lets you try it in about 10 minutes. The pricing page lists the full diagnostics for Singapore and across Asia. A bank that meets every ratio today can still change tomorrow, so repeat the check each quarter.

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About the author

Stéphane Jambu

President, EQOS Forecast Asia

Stéphane Jambu leads EQOS Forecast Asia and works as a consultant in e-commerce, search visibility, and AI. LinkedIn profile