Financial modeling

A model is an argument about how the business works, expressed in arithmetic. Its value is the argument, not the output precision.

Structure

Three separated layers, always:

1. Inputs — every assumption, in one place, each with a source and a date. An assumption buried inside a formula is invisible and therefore never challenged.
2. Calculations — no hard-coded numbers. Ever. A constant inside a formula is an untraceable assumption.
3. Outputs — the statements and the summary a decision-maker actually reads.

One row, one calculation, carried consistently across periods. Models become unauditable through inconsistent rows more than through complexity.

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