A bank is solvent when the value of what it owns is greater than the value of what it owes. That gap between assets and liabilities is the bank’s capital, and it is the cushion that absorbs losses before depositors are put at risk. Federal rules do not simply require positive capital; they require specific minimum ratios, the most closely watched being a Common Equity Tier 1 capital ratio of at least 4.5% of risk-weighted assets. When a bank slips below the required levels, regulators intervene on an escalating schedule that can end with the bank being closed and handed to the FDIC.
The Balance-Sheet Test
Solvency is a straightforward comparison. Add up everything the bank owns (loans, securities, cash, buildings). Add up everything the bank owes (deposits, borrowings, other liabilities). If assets exceed liabilities, the difference is positive equity and the bank is solvent. That equity is what takes the first hit when borrowers default or investments lose value. Losses come out of the shareholders’ cushion, not depositor funds.
When losses eat through the whole cushion and liabilities begin to exceed assets, the bank is insolvent. Selling every asset it owns would not raise enough cash to pay back everyone it owes. Regulatory capital requirements exist to keep banks well above that line, so that even a severe downturn does not push them over it.
Solvency Is Not the Same as Liquidity
These two get confused constantly and they describe different problems. Solvency is a long-term balance-sheet question: are assets worth more than liabilities? Liquidity is an immediate cash question: can the bank pay everyone who wants their money today?
A solvent bank can still face a liquidity crisis. If most of its assets are tied up in long-term loans or bonds that cannot be sold quickly, a sudden wave of withdrawals can leave it scrambling. That scramble often forces sales at steep discounts, which destroys capital and can push a solvent bank into insolvency. Silicon Valley Bank’s 2023 collapse followed this pattern. The bank held large amounts of long-term securities that had lost significant value as interest rates rose, and a $40 billion deposit run forced the issue before the bank could recover.1Board of Governors of the Federal Reserve System. Material Loss Review of Silicon Valley Bank
The reverse also happens. A bank can be sitting on plenty of cash and still be insolvent because its loan book has deteriorated so badly that liabilities exceed assets. Real stability requires both.
How Capital Is Measured
Capital ratios have two moving parts: what counts as capital (the numerator) and what the capital is measured against (the denominator).
Risk-Weighted Assets
Regulators do not simply add up everything a bank owns. Each asset gets a weight based on how likely it is to produce losses. Under the standardized approach set by the Basel framework, the weights follow a consistent logic:
- 0% for debt issued by highly rated sovereign governments, including U.S. Treasuries
- 20% for exposures to government-sponsored entities and highly rated banks
- 50% for claims on sovereigns and public sector entities with moderate credit ratings
- 75% for retail exposures like consumer loans and credit cards
- 100% for standard corporate loans and unrated exposures
- 150% for exposures to borrowers rated below B- or similarly high-risk assets
A bank holding $100 million in Treasuries and $100 million in corporate loans does not have $200 million in risk-weighted assets. The Treasuries contribute zero and the corporate loans contribute $100 million, so RWA is $100 million.2Bank for International Settlements. CRE20 – Standardised Approach: Individual Exposures Banks holding safer assets need less capital; banks loading up on risky loans need more.
Capital Tiers
Regulatory capital is sorted by how effectively each type absorbs losses. Common Equity Tier 1 is the highest quality, consisting primarily of common stock and retained earnings. It is permanent and fully available while the bank is still operating, so it takes losses first. Tier 1 capital includes CET1 plus Additional Tier 1 instruments, such as certain preferred stock that can absorb losses on a going-concern basis. Total capital adds Tier 2 instruments like subordinated debt, which can absorb losses only if the bank actually fails.
Each tier feeds a different ratio, and each ratio has its own minimum.
The Minimum Ratios Every Bank Must Meet
Federal banking regulators (the Federal Reserve, the FDIC, and the Office of the Comptroller of the Currency) translate the Basel international standards into binding U.S. rules. Every bank must maintain at least:
- 4.5% Common Equity Tier 1 capital ratio
- 6% Tier 1 capital ratio
- 8% total capital ratio
- 4% leverage ratio (Tier 1 capital divided by average total consolidated assets)
The first three use risk-weighted assets in the denominator. The leverage ratio does not, which prevents banks from making capital look artificially strong by shifting into low-weighted assets.3eCFR. 12 CFR 217.10 – Minimum Capital Requirements
The Capital Conservation Buffer
On top of those minimums, banks must hold a capital conservation buffer of 2.5% of risk-weighted assets, composed entirely of CET1. A bank that dips into the buffer faces escalating restrictions on dividends, stock buybacks, and discretionary bonus payments; the deeper it dips, the tighter the restrictions.4eCFR. 12 CFR 217.11 – Capital Conservation Buffer, Countercyclical Capital Buffer Amount, and GSIB Surcharge Including the buffer, a bank effectively needs a CET1 ratio of at least 7% to operate without payout restrictions.
Extra Requirements for the Largest Banks
Banks with $100 billion or more in assets face a supplementary leverage ratio of at least 3%. Unlike the basic leverage ratio, the SLR includes off-balance-sheet exposures like derivatives and credit commitments in its denominator.3eCFR. 12 CFR 217.10 – Minimum Capital Requirements The eight U.S. global systemically important banks face an enhanced SLR. A final rule taking effect in 2026 caps the enhanced SLR requirement for their depository institution subsidiaries at 4%.5Board of Governors of the Federal Reserve System. Agencies Issue Final Rule to Modify Certain Regulatory Capital Standards
G-SIBs also carry a capital surcharge that starts at 1% and scales up based on size, interconnectedness, cross-border activity, and complexity.6Federal Register. Regulatory Capital Rule (Regulation Q): Risk-Based Capital Surcharges for Global Systemically Important Bank Holding Companies Stacked with the minimum, the conservation buffer, and the countercyclical buffer (which U.S. regulators have kept at 0% since it was adopted in 2016, but which can add up to 2.5 percentage points), the biggest banks often need CET1 ratios well above 10%.
Stress Testing
Capital ratios describe the present. Stress tests ask whether the bank could still meet its minimums in a severe recession. The Federal Reserve runs annual tests on every bank holding company, savings and loan holding company, and intermediate holding company of a foreign bank with $100 billion or more in total consolidated assets.7Board of Governors of the Federal Reserve System. 2026 Stress Test Scenarios
The tests project losses, revenues, expenses, and capital under hypothetical conditions. The 2026 exercise uses a severely adverse scenario along with a global market shock component and a counterparty default component for the largest firms. The severely adverse scenario typically models a deep recession with sharp increases in unemployment, steep drops in asset prices, and significant market volatility. If projected capital would fall below required levels, regulators can restrict dividends and require the bank to raise more.8Board of Governors of the Federal Reserve System. Annual Large Bank Capital Requirements
Where Reported Ratios Can Mislead
Regulatory ratios are the primary solvency measure, but they have blind spots.
One is unrealized losses on securities. Under current U.S. rules, many banks can elect to exclude the effects of accumulated other comprehensive income from their regulatory capital. In practice, a bank can hold bonds that have dropped significantly in market value and still report capital as though those losses had not occurred. The losses are real economically but invisible in the regulatory numbers. Silicon Valley Bank used this opt-out, and its reported ratios looked healthy right up until a deposit run forced it to sell the depreciated securities and recognize the losses at once.1Board of Governors of the Federal Reserve System. Material Loss Review of Silicon Valley Bank
Market-based indicators sometimes flag concerns that reported ratios miss. Credit default swap spreads widen when investors perceive rising default risk. Equity prices and bond yields also carry information about how the market views a bank’s condition. None replace regulatory analysis, but they can serve as early warning when they diverge sharply from what the reported ratios suggest.
What Happens When a Bank Falls Short
Banks do not go bankrupt the way other businesses do. Federal law imposes a structured escalation that begins well before insolvency.
Prompt Corrective Action
When capital falls below required levels, the bank’s primary regulator places it into the prompt corrective action framework. Federal law sorts banks into five categories based on capital:
- Well capitalized. Significantly exceeds all minimums. No restrictions.
- Adequately capitalized. Meets all minimums. Some limitations on brokered deposits.
- Undercapitalized. Falls below any minimum. Must submit a capital restoration plan; regulators restrict asset growth, acquisitions, and new business lines.
- Significantly undercapitalized. Regulators can force management changes, restrict executive compensation, and require asset sales.
- Critically undercapitalized. Regulators must appoint a receiver or take other action within 90 days.
The system is designed to force intervention early. By the time a bank reaches the critically undercapitalized stage, regulators have already been restricting its operations for some time.9Office of the Law Revision Counsel. 12 USC 1831o – Prompt Corrective Action
Receivership
When a bank is closed, the FDIC is appointed as receiver. For federally chartered institutions, the appropriate banking agency appoints the FDIC directly. For state-chartered banks, the state supervisor typically makes the appointment, though federal regulators can step in under certain conditions.10Office of the Law Revision Counsel. 12 USC 1821 – Insurance Funds
The most common resolution method is a purchase and assumption transaction, where a healthier bank acquires the failed bank’s deposits and selected assets. For depositors, the transition is usually seamless. When no buyer can be found, the FDIC pays depositors directly from the insurance fund. Deposit insurance covers up to $250,000 per depositor, per ownership category, at each FDIC-insured bank. Joint accounts, retirement accounts, and trust accounts each qualify as separate ownership categories, so one person can hold well over $250,000 in insured coverage at a single bank if the funds are spread across different account types.11Federal Deposit Insurance Corporation. Understanding Deposit Insurance
Shareholders and unsecured creditors absorb losses first. Equity holders are wiped out entirely in a bank failure, and bondholders recover only what remains after insured depositors and other priority claims are paid.
Orderly Liquidation for the Biggest Firms
For the largest financial companies whose failure could threaten the broader economy, the Dodd-Frank Act created a separate resolution path called the Orderly Liquidation Authority. Before it can be used, the Secretary of the Treasury must determine both that the company is in default or in danger of default, and that its failure would pose a serious risk to financial stability. The FDIC then acts as receiver with special powers to wind down the firm in a controlled way rather than allowing a chaotic bankruptcy. To support this, G-SIBs are required to maintain minimum levels of total loss-absorbing capacity, ensuring they hold enough long-term debt and equity that losses can be absorbed during resolution without tapping public funds.12Bank for International Settlements. TLAC – Executive Summary