The Modigliani–Miller theorem — What It Is, and Where It…

What it does

In a world without taxes, bankruptcy costs or unequal information, the mix of debt and equity only divides the same cash flows differently. Its value in practice is as a checklist in reverse: financing matters exactly to the extent that taxes, the cost of financial distress and what managers know that investors do not break the ideal conditions.

Reach for it when: When a financing decision is being presented as if it created value by itself, and when someone argues that cheap debt makes a mediocre project good.
Where it stops: The conditions it assumes never hold, and it does not claim they do. It tells you where to look, not what the right amount of debt is.

Franco Modigliani & Merton H. Miller, “The Cost of Capital, Corporation Finance and the Theory of Investment”, American Economic Review, 1958.

Why it sits at Finance

Where the money is, where it comes from, where it is going, and whether there will be enough. Finance is the object that constrains every other one, usually silently.

A model is only useful when you reach for it at the right moment. This one answers a question that arises here — so it is filed here, and nowhere else. These are the working areas it serves:

BudgetingBudgeting practice, and the long-standing critique that annual budgets encode last year’s assumptions unless deliberately rebuilt.
ForecastingRolling forecast practice, developed partly in response to the annual budget’s tendency to be obsolete on publication.
Cash flowWorking capital management: the cash conversion cycle, and the standard finding that growth increases the gap between paying and being paid.
Financial reportingStatutory reporting requirements alongside management accounting’s different purpose: one is for compliance, the other for decisions.
Funding and capitalModigliani & Miller, “The Cost of Capital, Corporation Finance and the Theory of Investment”, American Economic Review, 1958; Myers & Majluf, “Corporate Financing and Investment Decisions When Firms Have Information That Investors Do Not Have”, Journal of Financial Economics, 1984 (the pecking order).
Investment appraisalJoel Dean, Capital Budgeting (1951), on discounted cash flow for project selection; Graham & Harvey, “The Theory and Practice of Corporate Finance: Evidence from the Field”, Journal of Financial Economics, 2001, on how NPV, IRR and payback are used side by side in practice.
TaxScholes & Wolfson, Taxes and Business Strategy: A Planning Approach (1992), on weighing tax against non-tax costs; the arm’s length principle in the OECD Transfer Pricing Guidelines (1995, revised since).

All of Finance

What it touches elsewhere

Nothing in a business is decided on its own. A conclusion reached with this model at Finance lands in these other cores, whether or not anyone follows it there.

Long term goalsAn acquisition chosen under Build, buy or ally is valued and later reviewed with the method in Investment appraisal.
Goal CoreResourcing decisions are made here; unfunded goals are goals in name only.
Business CoreMonetisation produces the revenue this object then has to manage.
Data CoreFinancial measures are the most reported and the most often confused with performance.
Time CoreRunway is a date, and it constrains every other date in the plan.

Filed at the same place

These answer questions that arise at Finance too. Where they disagree with this one, the disagreement is the useful part.

DuPont analysisBreak return on equity into margin, asset turnover and leverage, so the number says where it came from.
Break-even and cost–volume–profit analysisHow much has to be sold before the fixed costs are covered, and what each sale after that is worth.
Unit economicsWhat it costs to win one customer, set against what that customer is worth over the whole relationship.
Beyond budgetingReplace the fixed annual budget with rolling forecasts and targets set against actual conditions.
Net present value and discounted cash flowMoney received later is worth less than money received now, so future cash has to be discounted before it can be compared.
The pecking order theoryCompanies prefer internal funds, then debt, and issue new shares last — because outsiders read every financing choice as a signal.

Elsewhere in Business Core

These are other people’s models, named here so you can go to the source and use them properly. The Omnigoal is not affiliated with their authors and is not endorsed by them; nothing of theirs is reproduced here — no canvas, no diagram, no wording. Each is described in our own words, with the originator credited, because the framework is a place to put thinking, not a replacement for the people who did it. Model names and trademarks belong to their respective owners and are used here only to refer to the work itself.

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