How you allocate overhead decides every cost you report.
Indirect cost allocation is the single most consequential choice in your cost model. This question reveals whether overhead is spread on one crude rate, distorting every product and customer number, or assigned by the activities and time that actually consume it.
“How does your organization allocate indirect and overhead costs?”
How should indirect and overhead costs be allocated?
Overhead should be assigned by the activities and time that actually drive it, not spread on a single volume-based rate. A single plant-wide rate distorts product cost by 30% to 60% because complex, low-volume products absorb far less overhead than they truly consume. ABC and TDABC trace overhead through cost pools and drivers, so a product or customer carries its real share. The result is that cross-subsidies collapse and the true winners and losers in the portfolio finally become visible.
One crude rate hides the real cost of everything.
Indirect cost allocation determines the accuracy of every product cost, every customer profitability number, and every pricing decision. Get it wrong and every downstream figure inherits the error.
A single volume-based rate systematically overcosts simple, high-volume products and undercosts complex, low-volume ones. Traditional allocation distorts product cost by 30% to 60%, so the business believes some loss-makers are winners and prices them to attract more of the loss.
ABC and TDABC break overhead into cost pools and assign it through activity and time drivers. A complex product that demands more setups, inspections, and handling now carries that cost, and the portfolio’s true profit shape emerges for the first time.
Overhead moves from one bucket to traced cost.
As allocation matures, a single rate gives way to multiple pools and then to activity and time drivers, and the orange distortion band shrinks toward true cost, level by level.
What carries your overhead?
Question 1 assesses how far your allocation reflects the activities and time that actually consume overhead. Each level reflects a smaller gap between reported and true cost.
“We do not formally allocate overhead to products or customers.”
Overhead sits in a general pool and is never assigned, so product and customer costs include only direct cost. Every profitability number is incomplete, and decisions are made as if overhead did not exist.
- Product and customer costs exclude overhead entirely
- Margins look healthier than the business actually is
- No basis exists to compare products on full cost
- Pricing ignores the largest part of the cost base
“We add a single percentage of overhead over direct cost or volume.”
A single plant-wide rate is applied, usually as a percentage of labour, machine hours, or volume. It gives every product an overhead figure, but the rate is an average, so simple products are overcosted and complex ones undercosted by a wide margin.
- A single volume base drives all overhead allocation
- Complex, low-volume products are systematically undercosted
- Automation makes the labour base increasingly misleading
- Cross-subsidies hide inside a plausible-looking rate
“We use several cost pools and bases to match overhead to how it is consumed.”
Overhead is split into multiple pools, each assigned on a base that reflects its driver: machine hours for equipment cost, setups for changeover cost, orders for handling. Product costs are far closer to reality, and the worst cross-subsidies are corrected.
- Pools and drivers may still be coarse for some activities
- Time and capacity are not yet explicit in the model
- Maintaining many bases can become administratively heavy
- Some overhead may still ride on a volume proxy
“We assign overhead through activities and time using ABC or TDABC.”
Overhead is traced through activities and, in TDABC, through time equations built on a capacity cost rate. Each product, order, and customer carries the resource time it actually consumes, and the cost of unused capacity is reported separately rather than buried in product cost.
- Time equations need clean activity and capacity data
- Model complexity must be balanced against maintainability
- Unused-capacity cost must be governed, not reabsorbed
- The model must be refreshed as processes change
Practical steps, level by level.
Quick Wins
- Identify your total overhead and a simple base such as labour or machine hours
- Apply a single overhead rate so every product and customer carries a share
- Compare full cost to price and flag any line now below breakeven
- Show management the products whose overhead was previously invisible
Structural Improvements
- Split overhead into pools that map to distinct activities
- Choose a driver for each pool that reflects real consumption
- Reassign overhead through the pools and compare to the old single rate
- Act on the cross-subsidies the new view reveals
World-Class Practices
- Introduce TDABC time equations for the activities that drive most cost
- Set a capacity cost rate and report unused capacity as a separate line
- Trace overhead to products, orders, and customers by the time they consume
- Feed true cost into pricing, portfolio, and capacity decisions
Where allocation error hurts most.
The consequence of a crude rate differs by industry, but the direction is the same: the more complex the mix, the larger the hidden distortion.
| Industry | Distortion | Key Insight |
|---|---|---|
| Manufacturing | 30-60% | Product-mix complexity makes single-rate allocation worst here; TDABC corrects the systematic undercosting of custom, low-volume lines. |
| Distribution & Wholesale | Order-level | Warehousing, picking, and delivery are distinct pools; ignoring them buries the true cost of small, frequent orders. |
| Services | Time-driven | Overhead is largely people time; TDABC time equations assign it to cases and clients by the effort each really demands. |
Is your overhead traced, or just spread?
Take the free Profitability Health Check to assess how accurately your cost model assigns indirect cost, and where a single rate is quietly distorting every decision.