andreworia/model-architecture-template

Model Architecture Template

When to use

Use this skill at the very start of any new Excel model build -- before a single formula is written -- to establish the structural foundation. Trigger it when a team is starting a new model from scratch, when a model has been handed over from another team and needs to be restructured to a consistent standard, or when an organization wants to establish a house standard for all Excel models. It is the most upstream skill in the Modelling OS category and produces the empty architectural shell that all other skills populate.

What it does

Produces a complete master architecture for any new strategy or finance Excel model: the full tab set with naming conventions, purpose, and color labels; a conventions sheet defining color codes, font sizes, number formats, and structural rules; print area and page setup for every tab; and a version history system. This is the skeleton into which all content skills (DCF, Scenario Model, KPI Dashboard) are built.

Method

1. Define the universal tab set. Every strategy or finance model, regardless of its specific purpose, should include these structural tabs:

   Cover tab: Model identity and navigation. Legend/Conventions tab: Color codes, formatting rules, named range registry. Inputs tab: All user-editable assumptions. Data/Lookup tab: Reference tables, named ranges, lookup data. One or more Calc tabs: Named by workstream. Checks tab: Verification formulas, error flags. Outputs/Summary tab: Executive-facing summary, no calculations. Documentation tab: Model history, assumption rationale, audit log.

2. Design the Cover tab. The Cover tab is the first tab the user sees. It contains:

   Row 1-3: Model title (large font, bold), sub-title or client name (medium font), date range covered (small font). Rows 5-8: Key metadata: Version number, Last updated date, Prepared by, Reviewed by, Status (Draft/Final/Archived). Rows 10-15: Purpose statement (2-3 sentences describing what the model does and its primary audience). Rows 17-25: Key output summary (a 3-6 row table showing the model's headline outputs -- values referenced from the Outputs tab, not calculated here). Rows 27-35: Navigation guide -- a tab index showing every tab, its purpose, and a hyperlink to it. Rows 37-40: Confidentiality and disclaimer statement.

3. Design the Legend/Conventions tab. The Legend tab documents all structural rules used in the model. It serves as a guide for any user who did not build the model. Contents:

   Color code table: Color | Fill type | Meaning | Usage rule. Font convention table: Font type | Size | Usage (e.g., tab title: bold 12pt; section header: bold 10pt; body: regular 9pt). Number format table: Data type | Format string | Example (e.g., Currency: $#,##0.0 -> $1,234.5; Percentage: 0.0% -> 12.3%). Tab inventory: Tab name | Purpose | Color label | Status (Active/Archive). Named range registry: Named range | Refers to | Purpose | Last verified date. Structural rules: A bullet list of the model's architectural principles (no hardcodes in Calc tabs, all inputs on Inputs tab, etc.).

4. Define the color coding standard. Apply this consistently:

   Blue fill (#DDEEFF or custom), blue or dark blue font: Input cells (user-editable, hardcoded values). White fill, black font: Formula cells (never edit directly). Light green fill (#DDFFDD) or green font: Output cells and check cells that pass verification. Light grey fill (#F5F5F5): Section headers, spacers, non-active areas. Light orange fill (#FFE4B5): Override cells (temporary hardcodes, flagged for review). Red fill (#FFDDDD) or red font: Error flags, failed checks, alerts. Dark grey fill (#404040), white font: Tab-level headers and major section dividers. Tab color-coding: Inputs tab = blue tab; Data tab = grey tab; Calc tabs = no color (white); Checks tab = green tab; Outputs tab = dark grey tab; Cover and Legend = no color.

5. Define number format conventions. Apply globally using Excel's custom number format (Ctrl+1):

   Financial figures in $000s: #,##0 (no decimal); or #,##0.0 for one decimal. Financial figures in $M: #,##0.0 with "M" label in the column header. Percentages: 0.0% (one decimal, never 0% or 0.00% unless the context requires). Multipliers: 0.0x. Headcount: #,##0 (no decimal). Dates: MMM-YY for period headers (Jan-24, Feb-24); YYYY for year labels. Ratios: 0.00 (two decimals). Per-unit metrics (e.g., revenue per FTE): #,##0 with unit label in header.

6. Define the Calc tab naming convention. Each Calc tab name follows the pattern: [Category abbreviation] - [Description]. Maximum 25 characters. Category abbreviations: Rev (revenue), Cost (costs), FS (financial statements), Val (valuation), Mkt (market/TAM), Ops (operations), Cap (capital/investment). Examples: "Rev - ARR Build", "Cost - Headcount", "FS - Income Statement", "Val - DCF Engine".

7. Design the Checks tab. The Checks tab is the model's integrity layer. It should include:

   A summary traffic light at the top: IF(COUNTIF(checks_range,"FAIL")>0,"MODEL HAS ERRORS","ALL CHECKS PASS"), formatted in red or green respectively.

   Balance sheet balance check: Assets - Liabilities - Equity = 0 (IF(ABS(check)<0.01,"PASS","FAIL")).

   Cash flow tie-out: Opening cash + net cash flow - closing cash = 0.

   WACC vs. terminal growth rate: IF(WACC>terminal_growth,"PASS","FAIL -- WACC must exceed terminal growth").

   Probability sum check: IF(ABS(SUM(probabilities)-1)<0.001,"PASS","FAIL -- Probabilities do not sum to 100%").

   Revenue agreement: Revenue total in P&L tab = Revenue total in DCF tab (IF(ABS(difference)<0.1,"PASS","FAIL")).

8. Define the version control system. On the Cover tab, build a version history table: Version | Date | Changed by | Change summary. Start at v1.0. Increment the minor version for small updates (v1.1, v1.2), the major version for structural changes (v2.0). The version number in the Cover tab header should reference this table.

9. Set print areas and page setup for each tab. Define these settings:

   Cover tab: Portrait, A4, fit to 1 page. Print area: A1 to end of content. Legend tab: No print area required (internal reference document). Inputs tab: Portrait, A4, fit to 1-2 pages. Print area: all input sections. Each Calc tab: Landscape, A4, repeat row 1 on every page (Page Layout > Print Titles > Rows to repeat at top). Scale to fit width. Checks tab: Portrait, A4, fit to 1 page. Outputs tab: Landscape, A4, fit to 1 page. Print area: the full dashboard zone.

10. Establish the row and column structure standard. Apply these to every Calc tab for consistency:

    Row 1: Tab title (merged across columns, bold, dark fill, white font, 14pt). Row 2: Tab purpose statement (one sentence, italic, light fill). Row 3: Empty spacer row. Row 4: Section header (first section, bold, grey fill). Rows 5 onward: Data rows (row header in column A, data in columns B onward). Column A: Row labels (minimum 30 characters wide). Column B: First time period or first data column. Columns onward: Subsequent periods, scenarios, or categories. Last column: Total or summary column (bold, thin left border).

11. Set column widths and row heights. Column A (row labels): 28-35 characters wide. Data columns: 10-12 characters wide for annual data; 8-10 for monthly data. Header rows: 18-20pt height. Data rows: 15pt height. Section header rows: 18pt height. This creates a clean, scannable layout without wasted space.

12. Create a model startup checklist. When starting any new model using this a