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Capital Structure and Dividend Policy: Modigliani-Miller Explained

Updated 11 October 2026 · Fact-checked

Capital structure is the mix of debt and equity a firm uses. Modigliani-Miller shows that in perfect markets with no taxes, this mix does not change firm value, and dividend policy does not either. Real firms differ because of taxes, distress costs and information. To solve questions, state the assumptions first, then apply the correct proposition.

Understand Capital Structure and Dividend Policy

A firm raises money from shareholders (equity) and lenders (debt). The split between them is its capital structure. The ratio of debt to equity, or debt to total capital, is called gearing or leverage. The question is simple: can management make the firm worth more just by changing this split?

Modigliani and Miller (MM) answered in two steps. In their first case there are no taxes, no bankruptcy costs, no transaction costs, and everyone can borrow and lend at the same rate, with full information. Then Proposition I says the value of a firm depends only on its business cash flows, not on how it is financed. The reason is arbitrage. If a geared firm were worth more than an identical ungeared one, investors could create the gearing themselves by borrowing personally. This is called homemade leverage.

Proposition II says what happens to the cost of equity. Debt is cheaper than equity, but more gearing makes equity riskier, so shareholders demand a higher return. The extra cost of equity exactly offsets the cheaper debt, so the WACC stays constant. With debt that is risk-free, ke = k0 + (k0 − kd) × D/E. Here k0 is the cost of capital of an all-equity firm.

With corporate tax, where interest is tax deductible, MM change their view. Debt gives a tax shield, so a geared firm is worth more. In the simplest case with permanent, risk-free debt, the value rises by the tax rate times the debt. Taken to the extreme, this would suggest 100% debt. Real firms do not do this because of financial distress costs, agency costs and loss of flexibility. This leads to the trade-off theory of an optimal gearing level. The pecking order theory adds that firms prefer internal funds first, then debt, then new equity, because of information differences.

Dividend policy follows the same logic. MM's dividend irrelevance says that in perfect markets, value depends on investment decisions and earnings, not on how profit is split between dividends and retention. If a firm pays less, shareholders can sell shares to create cash (homemade dividends). The bird in the hand view argues investors prefer certain dividends to uncertain future capital gains, so high payout raises value. MM reply that the risk of the firm's cash flows is the same either way. Real-world factors such as taxes, transaction costs, clientele effects and signalling (dividend changes tell the market about management's view of the future) can make dividend policy matter in practice.

Key rules to remember

MM Proposition I (no tax): V_G = V_U; Value of a geared firm equals value of an identical ungeared firm. Holds only under the perfect market assumptions.
MM Proposition II (no tax, risk-free debt): ke = k0 + (k0 − kd) × D/E; Cost of equity rises linearly with the debt to equity ratio. D and E are market values.
WACC (no tax): WACC = ke × E/(D+E) + kd × D/(D+E) = k0; Unchanged by gearing in the no-tax case.
MM with corporate tax (permanent debt): V_G = V_U + t × D; t is the corporate tax rate and D the market value of permanent debt. Ignores distress costs.
Cost of equity with tax: ke = k0 + (k0 − kd) × (1 − t) × D/E; WACC falls as gearing rises because of the tax shield.
After-tax cost of debt: kd(1 − t); Used in WACC when interest is deductible.
Dividend irrelevance (no frictions): Value = PV of future free cash flows to investors, independent of payout; Ex-dividend share price falls by about the dividend paid in perfect markets.

How to solve Capital Structure and Dividend Policy questions

Use this method for both calculation and discussion questions on capital structure and dividend policy.

1Read the question and note whether taxes, distress costs and transaction costs are mentioned. This decides which MM version applies.
2State the assumptions you are using in one line, such as perfect markets, no tax, risk-free debt.
3Identify the data: market values of debt and equity, kd, ke or k0, tax rate, and any dividend details.
4Choose the formula: Proposition I or II for no tax, the tax-adjusted forms if tax applies.
5Calculate step by step, using market values and keeping rates as decimals. Check that WACC is consistent with your answer.
6Interpret the result: say what it means for firm value, shareholders or the cost of capital.
7For discussion parts, add the real-world limits: distress costs, agency costs, signalling, clientele effects, taxes on dividends and gains.
8Check that your conclusion matches your assumptions, for example no tax means no value change.

Quickest way: Three-line check for MM questions

When to use it: Use when time is short and the question asks for a cost of equity, WACC or the effect of a financing change.

Ask: is there tax? If no, WACC = k0 and value is unchanged.
Find ke from k0 + (k0 − kd) × D/E, adding (1 − t) if tax applies.
For tax, add t × D to the ungeared value. Then state one real-world limit in a sentence.

Common mistakes in Capital Structure and Dividend Policy

Saying MM Proposition I always holds, even with tax.
Students remember the headline result and forget it needs perfect markets.
Fix: Always state the assumptions. With corporate tax, value rises by t × D.
Using book values of debt and equity in D/E.
Balance sheet numbers are easier to find.
Fix: Use market values in MM and WACC calculations unless told otherwise.
Thinking cheaper debt lowers WACC in the no-tax case.
Students look at kd alone and ignore the rise in ke.
Fix: Show that ke rises by exactly enough, so WACC stays at k0.
Forgetting the (1 − t) factor in the cost of debt or Proposition II with tax.
Students mix the no-tax and tax formulas.
Fix: Write down whether tax is present before starting and use the matching formula.
Claiming dividend policy never matters in practice.
MM irrelevance is treated as a fact about real markets.
Fix: Say it holds in perfect markets, then discuss taxes, signalling, clientele and transaction costs.
Applying t × D when debt is not permanent.
The shortcut is memorised without its condition.
Fix: State that t × D assumes permanent, risk-free debt. Otherwise discount the tax savings over the debt's life.

Worked examples

Example 1

A firm has no tax. Its all-equity cost of capital k0 is 12%. It has debt of ₹40 crore at kd = 8% and equity of market value ₹60 crore. Using MM, find the cost of equity and the WACC. Assume risk-free debt.

Show the solution

Assumptions: perfect markets, no tax, kd constant.
D/E = 40 ÷ 60 = 0.6667.
ke = 12% + (12% − 8%) × 0.6667 = 12% + 2.667% = 14.667%.
Weights: E/(D+E) = 60/100 = 0.6, D/(D+E) = 0.4.
WACC = 0.6 × 14.667% + 0.4 × 8% = 8.8% + 3.2% = 12.0%.

Answer: ke ≈ 14.67% and WACC = 12%, equal to k0, as MM Proposition I implies.

Example 2

An ungeared firm has value ₹200 crore. Corporate tax rate is 25%. It issues permanent debt of ₹80 crore and uses the proceeds to buy back shares. Ignoring distress costs, find the value of the geared firm and comment.

Show the solution

Assumptions: MM with corporate tax, permanent risk-free debt, no distress costs.
Tax shield value = t × D = 0.25 × 80 = ₹20 crore.
V_G = V_U + t × D = 200 + 20 = ₹220 crore.
Equity value = 220 − 80 = ₹140 crore.
Comment: gain comes only from the tax shield. In practice, distress and agency costs reduce it, so the optimal gearing is below 100% debt.

Answer: Geared firm value = ₹220 crore, with equity of ₹140 crore. The ₹20 crore gain is the tax shield, which real costs of distress would partly offset.

Exam tips

Begin every answer with the assumptions. Markers often award marks for this alone.
In calculation questions, show the formula in standard notation, then substitute, then give the result with units.
For discussion parts, link each theory to its reason: trade-off to distress costs, pecking order to information, bird in the hand to uncertainty.
Keep the no-tax and tax cases separate. Label your working clearly.
For dividend questions, mention signalling and clientele effects to show you know why practice differs from MM.

Practice questions from Key principles of finance

Capital Structure and Dividend Policy in other exams

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

Capital Structure and Dividend Policy: frequently asked questions

What is the Modigliani-Miller theorem in simple words?

It says that in perfect markets, how a firm splits its funding between debt and equity does not change its total value. Value comes from what the business earns. Changing the mix only changes who bears the risk.

Why does the tax shield change the MM result?

Interest is deducted before tax, so debt reduces the tax paid. This saving adds value to the firm. In the simple case with permanent debt, the gain is the tax rate times the debt.

What is the difference between dividend irrelevance and bird in the hand?

Dividend irrelevance says payout does not affect value in perfect markets, because investors can create their own cash flow by selling shares. Bird in the hand says investors prefer certain dividends to uncertain capital gains, so higher payout raises value. MM argue the risk of the firm's cash flows does not depend on payout.

Why do firms not use 100% debt if debt has a tax benefit?

Higher debt raises the chance and cost of financial distress, and can create conflicts between lenders and shareholders. These costs offset the tax benefit at some point. This gives an optimal gearing level under the trade-off theory.