Would your modelsurvive a review?

01The purpose of the model, the decisions it supports and its intended users are written down inside the model.

A model with no stated purpose cannot be judged fit for it. · ICAEW · Purpose

02Inputs, calculations and outputs are kept on separate sheets or clearly separated, labelled areas.

Mixing them is the most common source of hidden errors and silent overrides. · ICAEW · Design

03Every sheet follows the same layout and the same timeline: the same period sits in the same column everywhere.

A shifted column on one sheet breaks every cross-sheet link without warning. · ICAEW · Design

04The model is no more complex than the decision requires, and nothing in it is hidden: no hidden sheets, rows, columns or grouped-away logic.

Complexity that the user cannot see is complexity the user cannot challenge. · ICAEW · Design

05No numbers are hard-coded inside formulas; every assumption sits in its own labelled input cell.

A number buried in a formula cannot be found, flexed or defended. · ICAEW · Inputs

06Inputs are visually distinct through consistent formatting, and only input cells are intended to be changed by the user.

Formatting is how a reviewer knows what they are allowed to touch. · ICAEW · Inputs

07Every input carries a unit, a source, an owner and the date it was last updated.

An assumption with no provenance cannot be defended in front of a board. · ICAEW · Inputs

08Alternative cases are run from a single scenario selector, with the base case preserved and never overwritten.

Without this, scenarios become copies of the file and drift apart within a week. · ICAEW · Inputs

09Formulas are short enough to read in the formula bar, and longer logic is broken into labelled intermediate steps.

A formula nobody can read is a formula nobody can check. · ICAEW · Calculations

10Each calculation row uses one formula, applied consistently across every period.

Consistency across the row is what makes a model auditable in seconds rather than days. · ICAEW · Calculations

11Balances are built as opening plus movements equals closing, in the same way for cash, debt, working capital and fixed assets.

Consistent roll-forwards are why the balance sheet balances by construction, not by luck. · ICAEW · Calculations

12The model contains no circular references, no links to other workbooks and no macros required to calculate.

Circularity, external links and macros all hide logic from the reviewer and break when files move. · ICAEW · Calculations

13A dedicated checks area exists, and a single overall error flag is visible from every sheet.

If the model can go wrong silently, it will. · ICAEW · Checks

14The balance sheet balances and cash reconciles in every period, and a check would fire if either stopped.

The balance check is the model's heartbeat. · ICAEW · Checks

15Sensitivity and stress tests have been run, and the outputs respond sensibly to extreme inputs.

A model that only works on the base case is a calculator, not a model. · ICAEW · Testing

16Someone other than the builder has reviewed the model, and their findings have been addressed.

Builders cannot see their own blind spots. Every serious model has a second pair of eyes. · ICAEW · Review

17A cover or guide sheet explains purpose, structure, key assumptions, limitations and how to use the model.

Documentation is what turns a personal spreadsheet into a business asset. · ICAEW · Documentation

18Version control is in place: consistent file naming, a change log inside the model and one clearly current version.

"Which version is this?" is the most expensive question in a board meeting. · ICAEW · Version control

19Changes are logged, re-tested and the checks re-run before a new version is released to users.

A change that skips the checks is a new error waiting to be found. · ICAEW · Change control

20A competent person new to the model could understand and run it within an hour.

Transparency is the whole point of the Code. This is the test of all the others. · ICAEW · Transparency