Workbook architecture

What you're learning

Input

The only sheet a person types into by hand — assumptions, raw entries. Nothing here should be a formula.

Data

Raw records, usually as a Table (I1) — never touched by hand once it's loaded, only ever appended to or refreshed.

Calculation

The formulas that turn Data into something useful — kept separate so a broken formula never contaminates the raw records.

Summary & Output

What a reader actually sees — PivotTables, dashboards, the final report. Everything here reads from Calculation; nothing here is typed by hand.

Assumption cells & named ranges

A rate, a fee, a cutoff date — stored once, in one visible cell, and named so a formula reads =Price*(1-DiscountRate) instead of a bare $F$2 nobody remembers the meaning of.

Documentation sheet

Where the workbook came from, what refreshes it, and what to check before trusting it — the difference between a workbook someone can hand off and one only you can run.

Version & refresh notes

A "last refreshed" date and a one-line refresh procedure, kept in plain sight — not buried in a cell comment three tabs deep.

When to split a workbook

Once a single file starts serving two audiences (say, raw ops data and an executive summary) with different refresh cadences or access needs, that's usually the signal to split it into two.