What Are Indirect Costs, Exactly?
Indirect costs are expenses that cannot be directly traced to a single product, client, or service – things like management salaries, IT infrastructure, quality control, finance, HR, facilities. In most companies, these represent 30–60% of total costs.
The question is never whether to allocate them. The question is how.
The Four Main Methods (and What They Hide)
1. Single Rate / Volume-Based Allocation
The simplest approach: pick one driver (usually revenue, headcount, or direct labour hours) and spread everything proportionally.
What it hides: A client generating €500K in revenue but requiring 3x the customer service touchpoints looks identical to a client generating €500K with minimal service demand. One is profitable. The other probably isn’t.
2. Departmental Rates
A step up – each department gets its own allocation rate. Better, but still ignores how much of each department’s capacity each product or client actually consumes.
3. Activity-Based Costing (ABC)
Costs are assigned to activities first, then to cost objects based on actual consumption of those activities. A product that requires 12 quality checks is allocated 12x more quality cost than one that requires 1.
The limitation: ABC requires significant data infrastructure and regular maintenance to stay accurate.
4. Time-Driven Activity-Based Costing (TDABC)
An evolution of ABC developed by Kaplan and Anderson. Instead of surveying employees about time allocation (which produces biased data), TDABC uses time equations to estimate the capacity consumed by each transaction type.
TDABC is the method we use in CostCTRL because it scales – you can model a complex operation with dozens of activity types without the interview burden of traditional ABC.
The Real Cost of Choosing Wrong
A manufacturing client we worked with had been allocating overhead using revenue as the single driver for 11 years. When we rebuilt their model using TDABC, three of their seven product lines flipped from profitable to loss-making. The products they had been prioritising in sales were the ones destroying margin.
This is not unusual. In our diagnostic work, we see this pattern in roughly 40% of mid-market companies.
How to Choose the Right Method
The right method depends on your cost complexity and data maturity:
- High cost complexity + low data maturity → start with improved departmental rates, plan for TDABC
- High cost complexity + high data maturity → TDABC
- Low cost complexity → ABC or even volume-based rates may be sufficient
The worst outcome is using a method that’s more sophisticated than your data supports – you’ll produce precise numbers that are precisely wrong.
A Simple Diagnostic
Ask yourself: if your two largest clients both generate the same revenue, could you tell within 48 hours which one consumes more of your indirect capacity? If the answer is no, your allocation method is costing you money.
The Profitability Health Check includes a dedicated Cost Allocation dimension that assesses your current method against six criteria. It takes 4 minutes and gives you a benchmark against companies in your sector.
Frequently asked questions
Why does the indirect cost allocation method change the answer?
Because indirect costs are 30-60% of total cost, the rule you use to spread them decides which products and customers look profitable. A single volume-based rate makes high-volume, simple work subsidise low-volume, complex work; activity-based and time-driven methods trace each cost to what actually consumes it, so the same business can show opposite margins depending only on the method chosen.
What are the main indirect cost allocation methods?
The four common methods are single-rate (volume-based), departmental rates, activity-based costing (ABC), and time-driven activity-based costing (TDABC). They increase in accuracy and in the effort to maintain them. Single-rate is simplest but hides the cost of complexity; TDABC uses time equations from operational data to assign cost by the minutes each product or customer actually consumes.
When is a single volume-based rate good enough?
A single rate is acceptable only when products and customers are genuinely similar in how they consume support – similar order sizes, similar service intensity, low product variety. The moment you have a mix of small and large orders, rush jobs, or very different service levels, a single rate systematically misprices the complex work and you need a driver-based or time-driven method.
How does TDABC improve indirect cost allocation?
TDABC replaces averaged overhead rates with time equations derived from real operational data, so indirect cost follows the minutes each activity actually takes. This exposes the true cost of small orders, returns, rush deliveries and manual handling that a volume rate smears evenly, giving an auditable cost per product, customer, service and channel that supports pricing and mix decisions.