Difficulty: Intermediate | Prerequisites: Basic understanding of static (planning) budgets, cost behaviour (fixed vs. variable costs), contribution margin format income statements.
In the real world, actual activity levels almost never match what was planned. This chapter tackles the problem head-on: how do you evaluate performance when the volume you budgeted for is not the volume you got? Flexible budgets solve this by recalculating what costs and revenues should have been at the actual activity level, giving managers a fair baseline for comparison. If you already understand static budgets and know the difference between fixed and variable costs, you are ready for this material.
A flexible budget adjusts the original (static) planning budget to reflect what actually happened in terms of volume, so you can separate "we sold more or fewer units than expected" from "we spent more or less per unit than we should have." Variances are split into activity variances (volume-driven) and revenue/spending variances (price- and cost-control-driven). This distinction is the whole point: it tells managers where to look.
Planning budget (static budget)
The budget prepared before the period begins, based on the expected level of activity. It does not change once set.
In simple terms, this is the "original plan" budget.
Flexible budget
An estimate of what revenues and costs should have been, given the actual level of activity for the period. It recalculates variable costs and revenues using actual volume but keeps the budgeted per-unit rates.
Think of it as: "What would we have budgeted if we had known the real sales volume in advance?"
Activity variance
The difference between the flexible budget amount and the planning budget amount. It arises solely because actual activity differed from planned activity.
In simple terms, this is the portion of any overall variance that is explained by volume alone.
Revenue variance
The difference between actual total revenue and what total revenue should have been per the flexible budget. Favourable (F) when actual revenue exceeds the flexible budget; unfavourable (U) when it falls short.
Think of it as: "Did we get a better or worse average selling price than expected?"
Spending variance
The difference between the actual cost and the flexible budget cost for a given line item. Unfavourable when actual cost is higher than expected; favourable when lower.
In simple terms, this tells you whether costs were controlled, after removing any volume effect.
Management by exception
A system where managers focus investigative effort on variances that are large enough to signal a real problem, rather than chasing every small difference. A 0.1% variance is likely noise; a 10% variance warrants a closer look.
Think of it as: "Don't chase pennies; chase the items that actually moved the needle."
Favourable variance (F)
A variance that, taken on its own, increases net operating income relative to the budget. Revenue above budget or cost below budget.
Unfavourable variance (U)
A variance that, taken on its own, decreases net operating income relative to the budget. Revenue below budget or cost above budget.
Note: "favourable" does not always mean "good." A favourable materials variance could mean the company skimped on quality.
Variance analysis follows a repeating loop:
Prepare a performance report in the accounting department, comparing actual results to what the budget predicted.
Analyse variances to identify which ones are significant.
Raise questions about the root causes of those significant variances.
Identify root causes through investigation.
Take corrective actions for the next period.
Begin the next period's operations, and the cycle restarts.
The cycle exists because variances on their own do not explain anything. They raise questions. The investigation answers them.
Managers compare actual results to the budget and focus only on significant deviations.
Small variances (e.g. 0.1% of an item's spending) are likely random and not worth investigating.
Larger variances (e.g. 10%) are more likely to signal a genuine problem or opportunity.
This saves management time by directing attention where it matters most.
The planning budget is set before the period and assumes a specific activity level. The flexible budget takes the same per-unit assumptions but plugs in the actual activity level after the fact.
Why this matters: comparing actual results to a static budget mixes two effects together, volume differences and cost-control differences. You cannot tell which one caused the variance. The flexible budget strips out the volume effect, leaving only cost-control variances.
Activity variances arise purely from the difference between actual volume and planned volume. They tell you the financial impact of selling more or fewer units than expected.
Key behaviour of fixed costs: when activity increases, fixed costs stay the same in total. This means net operating income rises faster than revenue, because the fixed-cost "base" gets spread across more units. Percentage changes in net operating income are ordinarily larger than percentage changes in activity. This is operating leverage at work.
Revenue variances
Calculated as actual total revenue minus flexible budget revenue.
Favourable if the average selling price exceeded the budgeted price.
Unfavourable if the average selling price fell below the budgeted price.
Spending variances
Calculated as actual cost minus flexible budget cost for each line item.
Unfavourable if actual cost exceeded the flexible budget cost.
Favourable if actual cost was below the flexible budget cost.
Note: spending variances compare actual costs to the flexible budget (not the static planning budget), so volume has already been accounted for.
A complete performance report lines up five columns:
Actual results
Revenue and spending variances
Flexible budget
Activity variances
Planning budget
This layout lets you trace any overall variance from the planning budget through to actual results in two steps: first the activity variance (volume effect), then the spending/revenue variance (cost-control/pricing effect).
This report gives a more valid assessment of performance than simply comparing actuals to the static budget.
Flexible budgets work in non-profits too, but revenue behaves differently. Revenue may include a fixed component (e.g. government funding, grants) and a variable component (e.g. ticket sales, fees). The formula becomes: Revenue = Fixed funding + (Price per unit x Quantity).
Flexible budget revenue = Budgeted selling price per unit x Actual number of units sold
Flexible budget variable cost = Budgeted variable cost per unit x Actual number of units
Flexible budget fixed cost = Same as the planning budget (unchanged by volume)
Activity variance = Flexible budget amount - Planning budget amount
Revenue variance = Actual revenue - Flexible budget revenue
Spending variance = Actual cost - Flexible budget cost
For non-profits: Revenue = Fixed funding + (Price per unit x Quantity)
Flexible budgets are standard practice in manufacturing, retail, and service businesses wherever output or sales volume fluctuates. A restaurant chain, for example, uses flexible budgets to evaluate each location: if one store served 20% more customers than planned, its food and labour costs should be higher, and it would be misleading to penalise the manager for "overspending" against a static budget.
The management-by-exception principle shows up in any large organisation's monthly variance review. Finance teams typically set thresholds (e.g. variances over 5% or over a certain dollar amount) that trigger investigation, rather than reviewing every line item.
Students often compare actual costs directly to the static planning budget and conclude costs were "out of control." The static budget assumes a different volume. You must compare to the flexible budget to isolate cost-control issues.
"Favourable" does not always mean "good." A favourable materials spending variance could mean lower-quality inputs were purchased, which may hurt the product down the line.
"Unfavourable" does not always mean "bad." An unfavourable revenue variance on a cost line might simply reflect higher volume (which is a good thing), and that effect belongs in the activity variance, not the spending variance.
Students sometimes assume net income changes proportionally with activity. It does not, because fixed costs stay constant. A 10% increase in units sold can produce a much larger percentage increase in net operating income.
Expect questions that give you a planning budget and actual results at a different volume and ask you to prepare a flexible budget performance report. You will need to recompute variable items at the actual volume.
Be ready to classify each variance as an activity variance or a spending/revenue variance, and label it F or U.
Know that fixed costs do not change in the flexible budget. Only variable costs and revenues are adjusted for actual activity.
Understand why comparing actuals to a static budget is misleading and be able to explain it in a short-answer question.
Non-profit revenue formulas (fixed funding + variable component) can appear as a twist on the standard flexible budget question.
True or False: A flexible budget uses the same per-unit cost assumptions as the planning budget but substitutes actual volume for planned volume. (True)
Fill in the blank: An activity variance is caused solely by the difference between ______ and planned activity. (actual activity)
True or False: Fixed costs in the flexible budget are adjusted for the actual level of activity. (False, fixed costs remain the same.)
True or False: A favourable variance always means management performed well. (False, it could reflect lower quality or other trade-offs.)
Fill in the blank: Spending variance = Actual cost minus ______ cost. (flexible budget)
Q: A company planned to sell 10,000 units at $50 each. It actually sold 12,000 units at $48 each. What is the flexible budget revenue, and what are the activity and revenue variances?
A: Flexible budget revenue = 12,000 x $50 = $600,000. Activity variance = $600,000 - $500,000 = $100,000 F (volume was higher). Revenue variance = ($48 x 12,000) - $600,000 = $576,000 - $600,000 = $24,000 U (average price was lower).
Q: Why is it misleading to compare actual results directly to the static planning budget?
A: Because two things differ at once: the activity level and cost/revenue control. A static comparison conflates volume-driven differences with price- or cost-control differences, so you cannot tell which factor caused the overall variance.
Q: A cost has an unfavourable spending variance. Does that necessarily mean the manager did a poor job controlling costs?
A: Not necessarily. The variance might reflect an uncontrollable price increase (e.g. a supplier raising raw material prices), or it could mean the original budget assumption was unrealistic. Investigation is needed.
Q: Explain why percentage changes in net operating income tend to be larger than percentage changes in activity.
A: Fixed costs do not change with volume. When activity rises, variable costs rise proportionally but fixed costs stay flat, so each additional unit's contribution margin flows straight to net operating income. This leverage effect amplifies percentage changes in income relative to percentage changes in volume.
Q: In a non-profit organisation, how does the flexible budget handle revenue that includes both a fixed grant and variable fees?
A: The fixed grant stays the same in the flexible budget (just like any fixed cost). The variable fee component is recalculated at actual volume. Total flexible budget revenue = Fixed funding + (Budgeted price per unit x Actual quantity).
This connects directly to Chapter 10 (Standard Costs and Variances), which drills deeper into the spending variance by breaking it into price and quantity components for materials, labour, and overhead. The flexible budget is the bridge between the static budget covered in earlier chapters and the detailed standard cost variance analysis that follows.
The concept of operating leverage (fixed costs amplifying income changes) ties back to cost-volume-profit (CVP) analysis from earlier in the course. If you are comfortable with CVP, the behaviour of fixed costs in the flexible budget should feel familiar.
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