davekilleen/variance-analysis

When to use

Use when a finance or leadership user needs an evidence-backed explanation of actuals against an approved budget or forecast for a named period, category, or total. Confirm the comparison period and basis before calculating.

Do not use this skill to post or reclassify ledger entries, change a budget or forecast, approve corrective action, or provide audit sign-off. Not for close-status tracking, tax advice, or a financial decision made on behalf of a human owner.

Inputs and source discipline

1. Capture the period, comparison basis, metric definition, actual source, budget/forecast source,

source dates, date checked, and explicit as-of date. Record unit, currency, sign convention, and time window for every input; never invent a missing date or denominator.

1. Prefer reconciled ledger or close-package actuals, then an approved budget or forecast, then

dated operational reports, then dated context in meeting notes. A narrative explanation is not evidence of a number. Preserve source hierarchy and contradictory inputs.

1. Validate that actual and comparison values measure the same category, period, unit, currency,

accounting basis, and aggregation. Convert only with a cited rate or rule and date; otherwise mark the comparison not comparable rather than forcing a result.

Method

1. Work read-only and state the formula before computing: for example, dollar variance as

actual - comparison, and percentage variance as variance / absolute comparison only when the denominator is non-zero and that convention is authorized. Preserve the sign and state how favorable/unfavorable is determined for revenue versus expense; never flip signs to make a result look better.

1. Recalculate each category and reconcile the category variances to the supplied total,

allowing only documented rounding. Investigate missing categories, scope differences, and duplicate rows; if totals cannot reconcile, report the total as unknown or contradictory.

1. Apply the supplied materiality threshold in both amount and percentage terms when available.

If no threshold is supplied, state that materiality was not assessed; do not invent a cutoff or call a result material solely because it is visually large.

1. For each material or requested variance, classify the cause as timing or permanent only

when dated evidence supports it. Label a plausible but unverified explanation hypothesized, and use unknown when evidence does not establish a cause. Keep corrective actions as recommendations for human review.

Truth and uncertainty rules

Use observed for a value or event directly supported by a cited source, inferred for an interpretation, unknown for missing evidence or an untestable cause, stale for evidence outside the requested period or freshness, and contradictory when credible sources disagree. Show confidence and its basis. Never invent dates, metrics, owners, intent, money, percentages, causes, status, or evidence. A recommendation is not a human decision.

Output contract

Return an analysis containing:

• period, comparison basis, as-of date, units, currency, formula, denominator, and sign rule;
• a category table with actual, comparison, dollar variance, percentage when valid, source/date,

confidence, and comparability status;

• the materiality rule or an explicit not-assessed state;
• reconciled totals with rounding/scope differences called out;
• each cause labeled observed, inferred/hypothesized, timing, permanent, unknown, stale, or

contradictory, with supporting source evidence; and

• source register, unknowns, contradictions, limits, and recommendations clearly separate from

facts. Do not present an unverified cause as the explanation.

Safety and write boundaries

Remain read-only by default. Do not edit ledgers, budgets, forecasts, source notes, or reports. If a write, export, shared artifact, or other action is requested, preview the exact target, changes, and side effects; redact secrets or unapproved personal/confidential content; wait for explicit confirm from the responsible human authority; then perform only the approved action.

Verification and recovery

Read back every input and calculated row, recompute the formula independently, and reconcile category totals to the supplied total. Check sign, units, currency, period, denominator, source dates, and as-of scope; fail closed on any mismatch. If a source read or calculation fails, preserve the draft, mark the affected result unknown or blocked, record the failure, and rerun after correction. Never silently overwrite a contradictory total or promote a hypothesis to fact.