R006 — Propagated Errors

Purpose¶

R006 detects any cell in the workbook whose last calculated value is an Excel error — a formula that is currently returning #REF!, #VALUE!, #DIV/0!, or one of the other standard Excel error values. Unlike rules that infer a pattern across a row, R006 checks a single, directly observable fact per cell: does this cell's cached value indicate an error.

Detection Logic¶

R006 evaluates every node in the workbook's formula graph — every formula cell and every hardcoded cell alike — and flags any cell whose recorded error state is set. One finding is produced per affected cell. Because error state is read directly from the workbook rather than inferred from a comparison against other cells, this rule requires no minimum sample size and no dominant-pattern threshold: a single cell in error is sufficient to trigger a finding.

Why It Matters¶

An error confined to a single cell rarely stays confined. Because formulas commonly reference other formulas, one cell's error value typically propagates through every downstream calculation that depends on it, directly or indirectly — a single broken lookup on an assumptions tab can silently turn into dozens of downstream error values, or, if wrapped in error-masking logic elsewhere in the model, into a silently substituted default value that looks like a legitimate number. R006's fact — this cell currently evaluates to an error — is unambiguous in a way few other findings in the engine are, which is part of why it is one of five rules capable of capping a model's overall letter grade under the SM-2.0 Scoring Methodology, regardless of how high the model's numeric score otherwise is.

Evidence Produced¶

A triggered R006 finding's evidence identifies the specific sheet and cell address of the error, the exact error value the cell evaluates to, and a description stating that the cell currently evaluates to that error — a direct, observable fact rather than an inferred judgement. See the Finding Data Model & Confidence page for the full evidence and provenance model this finding is built on.

Severity¶

Critical. Weight 9.0. R006 is one of five critical-override rules under SM-2.0 (alongside R001, R002, R004, and R023): if it triggers even once, the model's overall letter grade is capped below A or B regardless of the numeric score the weighted formula produces. Confidence on every R006 finding is high, since error state is a deterministic fact rather than an inferred pattern.

Example¶

Trigger. A formula on a Debt Schedule worksheet reads =Revenue!C12/Revenue!C13, and the referenced denominator cell currently evaluates to zero, so the cell's cached value is #DIV/0!. R006 flags this cell directly: its recorded value is an error state.

Non-trigger. The same formula, but the denominator cell holds a nonzero value, so the division resolves to an ordinary numeric result with no error state. R006 does not fire, regardless of whether the result itself is otherwise reasonable — that judgement belongs to other rules and to manual review, not to R006.

Recommended Remediation¶

The root cause of the error is investigated and corrected at its source — the broken reference, the divide-by-zero condition, or whatever upstream fault produced the error value — rather than suppressed with error-masking logic (a distinct pattern the engine addresses separately). Once the source is fixed, every downstream cell that depended on the error value should be re-checked, since a fixed source can change previously error-masked or stale downstream values.

Related Rules¶

R006 shares the Structural taxonomy category with R001, R002, and R004, each published in this same initial phase of the Rule Reference; the remaining Structural-category rules follow in later phases and are indexed on the Rule Reference page as they are published.

Related Articles¶

• Formula Error Types in Financial Models — the Knowledge Centre's buyer-facing reference to the principal categories of formula error, including the visible error values this rule detects.

Version History¶

No version-specific changes to R006's severity, weight, or category are recorded as of engine version 2.1.0. This section will be updated in the same edit as any future change to the rule's declared attributes.