FRM Exam Part II · Capital Structure in Banks

Bank Capital Structure and the Role of Capital in Banks

Updated 11 October 2026 · Fact-checked

Bank capital structure is the mix of equity, debt and deposits that funds a bank's assets. Capital is the loss-absorbing equity cushion. It protects depositors and creditors, limits failure risk, and restrains risk-taking. To solve questions, compute leverage, find the loss that wipes out equity, and compare return on equity with risk.

Understand Bank Capital Structure and Role of Capital

A bank funds its assets with deposits, wholesale funding (repo, commercial paper, bonds), subordinated debt and equity. Equity is the smallest slice. Most of the balance sheet is borrowed. That is why banks are highly leveraged.

Capital is the part of funding that absorbs losses first. If assets fall in value, equity takes the hit before depositors and senior creditors. When losses exceed equity, the bank is insolvent. So the equity cushion is the bank's defence against failure.

Why hold equity at all, when debt is cheaper? Equity is costlier because shareholders bear first loss and demand a higher return. Banks would prefer less of it. Regulators force a minimum because failure imposes costs on others: depositors, deposit insurers and the wider system. Capital also aligns incentives. Owners with more at stake take less excessive risk, which reduces moral hazard linked to deposit insurance and implicit government support.

Leverage magnifies both return and risk. With a small equity base, a modest change in asset return causes a large change in return on equity. Higher leverage raises expected ROE when assets earn more than the cost of debt, but it also raises the chance that losses exhaust equity.

Keep three capital ideas apart. Book capital is the accounting value of equity (assets minus liabilities). Regulatory capital is the amount that qualifies under Basel rules, such as Common Equity Tier 1 after deductions. Economic capital is the bank's own estimate of the capital needed to cover unexpected losses at a chosen confidence level, such as the level consistent with a target credit rating. A capital buffer is capital held above the minimum, so the bank can absorb losses without breaching requirements.

Key formulas to remember

Balance sheet identity: Assets = Liabilities + Equity; Equity is the residual. Book capital = Assets − Liabilities.
Leverage multiple: Leverage = Assets ÷ Equity; Also called the equity multiplier. Inverse is the equity-to-assets ratio.
Equity ratio: Equity ratio = Equity ÷ Assets; Loss as a share of assets that wipes out equity, ignoring other effects.
Return on equity: ROE = Net income ÷ Equity = ROA × (Assets ÷ Equity); Leverage scales ROA into ROE. Losses are scaled the same way.
ROE with funding cost: ROE = [r_A × A − r_D × D] ÷ E, where D = A − E; Ignores taxes and costs. Use when asset yield and debt cost are given.
Economic capital: Economic capital ≈ Unexpected loss at a confidence level = Loss quantile − Expected loss; Expected loss is covered by pricing and provisions. Capital covers the unexpected part.
Capital buffer: Buffer = Actual capital ratio − Required minimum ratio; Positive buffer means room to absorb losses before breaching the requirement.

How to solve Bank Capital Structure and Role of Capital questions

Use this order for any question on bank capital structure, leverage or the role of capital.

1Read what is asked: a ratio, a loss threshold, an ROE change, or a concept (book vs regulatory vs economic capital).
2Write the balance sheet: Assets, Liabilities, Equity. Fill the missing item using Assets = Liabilities + Equity.
3Compute leverage (Assets ÷ Equity) and the equity ratio (Equity ÷ Assets).
4For loss questions, convert the asset loss to a percentage of assets and compare it with the equity ratio. Equity is wiped out when the loss reaches Equity.
5For return questions, compute net income first, then divide by equity. Check by using ROA × leverage.
6For concept questions, identify which capital definition is meant and who bears the loss first.
7Interpret: say whether higher leverage raised return, risk or both, and name the trade-off.
8Sanity check units and sign: losses reduce equity, and equity cannot go below zero in a limited-liability reading.

Quickest way: Leverage shortcut: scale by assets ÷ equity

When to use it: Use for questions asking how a small change in asset value or ROA changes equity or ROE.

Compute leverage L = Assets ÷ Equity.
Multiply the percentage change in assets (or ROA) by L to get the percentage change in equity (or ROE).
For the break-even loss, take 1 ÷ L as the percentage asset fall that wipes out equity.
Eliminate options that confuse book, regulatory and economic capital before calculating.

Common mistakes in Bank Capital Structure and Role of Capital

Treating equity as an asset or as cash the bank holds.
The word capital sounds like money set aside.
Fix: Capital is a funding source on the liability side. It says how assets are financed, not what the bank holds.
Dividing equity by equity ratio the wrong way, using Equity ÷ Assets as leverage.
Both ratios use the same two numbers.
Fix: Leverage = Assets ÷ Equity (greater than 1). Equity ratio = Equity ÷ Assets (less than 1).
Saying economic capital equals book capital.
Both are called capital and both are amounts in currency.
Fix: Book capital is accounting equity. Economic capital is a model-based requirement for unexpected losses at a confidence level. Compare them to judge adequacy.
Including expected loss in economic capital.
Students take the full loss quantile.
Fix: Expected loss is covered by pricing and provisions. Economic capital is the quantile minus expected loss.
Claiming more capital always lowers ROE because equity is costly, without conditions.
Mechanical reading of ROA × leverage.
Fix: More equity lowers leverage and, holding ROA fixed, lowers ROE. It also lowers risk. Say both.
Forgetting the buffer is measured above the requirement, not above zero.
Mixing actual ratio with the buffer.
Fix: Buffer = actual ratio − required minimum. Use this when judging headroom.

Worked examples

Example 1

A bank has total assets of $200 billion and equity of $10 billion. (a) Find its leverage. (b) By what percentage must asset values fall to wipe out equity? (c) If ROA is 0.60%, what is ROE?

Show the solution

Leverage = 200 ÷ 10 = 20.
Equity ratio = 10 ÷ 200 = 5%.
An asset fall of $10 billion equals 10 ÷ 200 = 5% of assets, which erases equity.
ROE = ROA × leverage = 0.60% × 20 = 12%.
Check: net income = 0.006 × 200 = $1.2 billion; 1.2 ÷ 10 = 12%.

Answer: Leverage is 20; a 5% fall in asset values wipes out equity; ROE is 12%.

Example 2

A bank holds assets of $100 billion funded by $92 billion of liabilities. Assets yield 5% and liabilities cost 3.5%. Ignoring taxes and costs, compute ROE. Then the bank raises equity to $12 billion, using it to repay debt, with assets unchanged. Compute the new ROE.

Show the solution

Initial equity = 100 − 92 = $8 billion.
Initial income = 5% × 100 − 3.5% × 92 = 5.00 − 3.22 = $1.78 billion.
Initial ROE = 1.78 ÷ 8 = 22.25%.
New equity = $12 billion, so liabilities = 100 − 12 = $88 billion.
New income = 5.00 − 3.5% × 88 = 5.00 − 3.08 = $1.92 billion.
New ROE = 1.92 ÷ 12 = 16.0%.
Interpretation: leverage fell from 12.5 to 8.33, so ROE fell, but the loss needed to wipe out equity rose from 8% to 12% of assets.

Answer: ROE falls from 22.25% to 16.0%, while the loss absorption cushion rises from 8% to 12% of assets.

Exam tips

Questions often ask for both the return effect and the risk effect of leverage. Give both.
Be exact on the three meanings of capital: book, regulatory and economic. Options are built to blur them.
Do the quick scaling check (loss ÷ equity ratio) before building a full balance sheet.
Watch the direction of the ratio: leverage above 1, equity ratio below 1.
Link capital to moral hazard and deposit insurance when the question asks why banks hold capital.

Practice questions from Capital Structure in Banks

Bank Capital Structure and Role of Capital in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Bank Capital Structure and Role of Capital: frequently asked questions

Why do banks hold capital above the regulatory minimum?

A buffer lets the bank absorb losses without breaching requirements, which could trigger restrictions on dividends and bonuses. It also reassures markets and keeps funding costs lower. Banks often target a level their own economic capital model supports.

What is the difference between book capital and economic capital?

Book capital is accounting equity: assets minus liabilities. Economic capital is the bank's model-based estimate of capital needed to cover unexpected losses at a chosen confidence level. If book capital is below economic capital, the bank is under-capitalised by its own standard.

Does higher leverage always raise ROE?

No. It raises ROE only when asset returns exceed the cost of debt. When asset returns are low or negative, leverage magnifies losses and ROE falls sharply. It always raises the probability that losses exhaust equity.

Why is equity more expensive than debt for a bank?

Equity holders bear losses first and are paid last, so they require a higher return. Debt has priority and, for deposits, may be insured. Banks therefore prefer lower equity, which is why regulation sets minimums.