Services

The workbook nobody else can open

Somewhere in your finance function there is a spreadsheet with forty tabs, twelve years of accumulated logic, and exactly one person who understands it. It produces a number the board relies on. Nobody has tested it since 2019 and everybody knows this is a problem.

Which workbook?

Tell us what it produces and how long it takes each month. We will scope replacing it.

1 / 3
$10,000–$28,000 typicalTested against its own historyThe expert stays involved
Extractread source, no writesMapaccounts, customers, vendorsLoadinto a staged tenantReconciletrial balance, per periodgate · must tieReviewyour controller signsCut oversource goes read-onlygate · must tievariance → back to mapping, never waivednothing advances past a gate until the trial balance agrees to the penny

The situation

The workbooks we usually replace

Different businesses, same pattern: high stakes, high complexity, single owner.

The consolidation

Multiple entities combined by hand, intercompany eliminated from memory, foreign currency applied at a rate somebody looked up. Monthly, under time pressure, at the end of the close.

Revenue schedules

Contract terms interpreted into a deferral schedule, maintained across amendments, reconciled to billing. The most audited spreadsheet in most companies.

Commissions

Tiers, splits, clawbacks, and accelerators, computed monthly and disputed regularly because nobody outside finance can verify it.

The management pack

Rebuilt every month from the same four exports, with the same pivot tables, by somebody whose time is worth considerably more.

The rolling forecast

Driver-based, several scenarios, updated monthly, and structurally unable to compare what was forecast against what happened.

The allocation model

Overhead pushed to departments or projects by a formula agreed years ago that four people now describe differently.

Spreadsheets are not the problem

Excel is excellent. The problem is not the tool — it is that a critical, complex, frequently-run calculation ended up somewhere with no version control, no test suite, no audit trail, no access control, and exactly one person who can maintain it.

Every one of those absences is survivable individually. Together, in a workbook the board relies on, they constitute a genuine business risk that everybody acknowledges and nobody has time to address.

The risk is not the spreadsheet. It is that the calculation it performs has no tests, no history, and one maintainer.

Extraction is archaeology

The logic in a mature workbook is rarely documented and frequently not what anybody believes it to be. There are hard-coded adjustments from a prior year, exceptions for a customer who left, formulas that differ in one column of one tab, and at least one number nobody can explain that everyone works around.

Finding those requires reading the workbook cell by cell, and it takes longer than the build. It is also frequently the most valuable part of the engagement, because several of the discoveries are errors.

Tested against its own history

The replacement is validated by running it against twenty-four months of historical inputs and comparing to what the spreadsheet produced. Every difference is investigated before launch and resolved into one of three categories: the replacement is wrong, the spreadsheet was wrong, or a rule changed and neither is wrong.

All three occur. On a typical engagement several months show differences, and more of them turn out to be spreadsheet errors than replacement errors — which is uncomfortable and is the reason the test exists.

Keep the expert

The person who owns the workbook is the domain expert, and replacement projects that treat them as an obstacle fail. They know the exceptions, they know why the odd adjustment is there, and they are the only reliable validator of the result.

What changes is what they spend the time on. Rebuilding the mechanics monthly becomes reviewing exceptions and explaining variances, which is the work they were hired for.

Where to start

How it runs

01

Read the workbook

Cell by cell, with the owner. Every rule, exception, hard-coded value, and inconsistency documented. Longer than you would expect and the most valuable phase.

02

Agree the rules

Including the ones that turn out to be wrong. Some decisions get escalated here because the spreadsheet was quietly making them on the business’s behalf.

03

Build and back-test

Run against twenty-four months of history, every difference investigated and categorised before anyone signs off.

04

Parallel run, then switch

Both run side by side for two cycles. The spreadsheet is retired when it has agreed twice, not on a target date.

Questions

What people ask.

What does it cost?
$10,000 to $28,000 depending on complexity. Reading the existing workbook is usually a third of it.
What if the spreadsheet is wrong?
The back-test finds it, and it happens more often than the reverse. We will tell you what we found and let you decide how to handle prior periods.
Do we lose flexibility?
For genuine ad-hoc analysis, keep using Excel — it is the right tool. What gets replaced is the monthly production run, not the ability to explore.
What happens to the person who owns it?
They stay central to the process. Their time moves from rebuilding mechanics to reviewing exceptions, which is the work they were hired to do.
How long is the parallel run?
Two full cycles, and the spreadsheet retires when the numbers have agreed twice rather than on a date in a plan.

Retire the workbook safely.

Tell us what it produces and who maintains it. We will scope replacing it without losing the logic.