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A variance is the difference between what you planned and what happened. This guide explains how to read one correctly, how to judge whether it matters, how to follow a waterfall, and how to chase a gap down to its cause. It applies anywhere variance appears: Comparison Center, Briefs, and Financial Performance.

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Reading a Single Variance

A variance is always comparison minus base. Base is what you measure against (budget, target, or a prior version); comparison is what you are testing (actuals or the live forecast).
Sign alone does not tell you good or bad. On a cost line, spending more than budget (a positive variance) is unfavorable. On a revenue line, earning more than plan (also a positive variance) is favorable. Always read variance by cost direction.

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When Is a Percent Material?

There is no single threshold, but a practical way to judge materiality is to weigh three things together: the percent, the absolute dollars, and whether the line is volatile by nature.
  • A small percent on a large line can still be a large dollar amount worth explaining.
  • A large percent on a tiny line is often noise, not a story.
  • A line that swings every period (timing-sensitive accruals, for example) tolerates a wider band than a stable, predictable line.
As an illustrative rule of thumb only, many finance teams flag anything beyond roughly 5 to 10 percent on a material line for review, tighten that band on stable lines, and loosen it on naturally lumpy ones. Use your own plan’s tolerance; the point is to read percent and dollars and line behavior together, never percent alone.
A 12% variance is not automatically bad. On a small or volatile line it may be expected. On a large, stable cost line it is usually worth a look. Judge it against the dollar size and the line’s normal behavior.

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Reading a Waterfall

A waterfall (also called a bridge) decomposes a single change into named movements, so an ending number becomes a story. Read it left to right: The green bars build up from the blue beginning anchor, the red bars pull back down, and they net to the blue ending anchor. A correct waterfall always reconciles: beginning plus the green minus the red equals the ending. If it does not net, the beginning balance is usually being mis-counted as a movement instead of anchoring the bridge.

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Common Variance Drivers

When a cost variance is decomposed (for example in a headcount brief), the named buckets explain the cause:
A large residual bucket is a signal, not an answer. It usually means the variance is concentrated in a dimension the decomposition did not name, so drill into it rather than accepting it.

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Drilling to Root Cause

1

Start at the headline

Read the total variance and its direction. Confirm it is material by dollars and percent together.
2

Find where it concentrates

Pivot by department, account, or entity in Data Explorer to see which slice carries the gap.
3

Drill to the transactions

Open the line to the individual transactions, including vendor and memo, so the cause is a specific posting, not an abstraction.
4

Name it

Tie the gap to a driver (rate, volume, mix, fringe, FX) so it can be explained in one sentence, then capture it in a Brief.

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If the Numbers Look Off

  • A variance that will not reconcile is almost always a scope mismatch: confirm both sides cover the same entity and period.
  • A blank on one side means that account or department is not mapped in that version, not a true zero.
  • Two surfaces that disagree usually differ on universe (for example GL P&L versus a domain cost model), which overlap but measure different things, so the gap is the universe difference, not an error.
When you have read the variance and named the driver, generate a Brief to write the story, or return to Comparison Center to widen or narrow the scope.