Throughput Accounting Notes (TOC; TA) - Comprehensive Study Notes

What is Throughput Accounting (TA)

Throughput Accounting is a modern accounting technique aligned with the Theory of Constraints (TOC).
Objective: maximize the rate at which money is generated from sales (Throughput), not minimize costs.
Throughput is defined as the rate at which money is generated from sales:
\text{Throughput} = \text{Sales Revenue} - \text{Direct Material Cost}
In TA, only direct material is treated as a variable cost; all other costs (labor, overheads, etc.) are treated as Operating Expenses (fixed in the short run).

Theory of Constraints (TOC) – Overview

A production and operations management approach.
Assumes every system has at least one constraint (bottleneck) that limits performance/output.
TOC aims to maximize throughput by managing the bottleneck effectively.

Key Concepts in Throughput Accounting

1) Throughput

The rate at which money is generated from sales.
Formula: Throughput = \text{Sales Revenue} - \text{Direct Material Cost}
Direct material is the only variable cost; other costs are fixed in TA.

2) Operating Expenses

All costs other than direct materials, including:
- Direct labor
- Overheads
- Factory expenses
- Indirect materials
In TOC these are treated as fixed costs (short run).

3) Bottleneck (Constraint)

A limiting factor/resource that restricts the output or throughput of the entire system.
🚧 Types of Bottleneck Resources:
- Production-related: limited machine capacity, skilled labor shortage
- Sales-related: limited sales staff, low market demand
- Supply-related: unreliable material suppliers
- Customer-related: on-time delivery requirements
- Price-related: uncompetitive prices reduce sales

Production Scheduling under TOC – Key Principles

1) Production must match the bottleneck’s capacity.
2) All other resources will have idle time — this is acceptable.
3) Only the bottleneck resource must be fully utilized.
4) Non-bottleneck overproduction is wasteful.
5) A small buffer inventory should be kept before the bottleneck to prevent delays.

How to Increase Throughput: Elevating the Bottleneck

Elevating the Bottleneck means increasing the capacity of the limiting resource.
Examples:
- Add overtime shifts or extend working days.
- Perform maintenance during off-hours.
- Shift skilled labor to bottleneck tasks.
- Use automation or process improvements (if affordable).

Goldratt’s 5-Step Process (TOC Cycle)

✅ Step 1: Identify the Constraint

Find the bottleneck or weakest link in the system.
Could be:
- A machine with limited capacity
- A shortage of skilled labor
- A supply chain delay
- Market demand limitations
Why? You can’t improve the system unless you know what’s holding it back.

✅ Step 2: Exploit the Constraint

Use the bottleneck to its maximum capacity without spending more.
Ensure:
- It’s never idle
- It works on high-priority tasks
- No time is wasted (e.g., waiting for materials)
Why? Maximize output from the resource that’s already limiting performance.

Step 3: Subordinate Everything Else

Align all other processes to support the bottleneck.
Avoid overproducing in non-bottleneck areas.
Prevent inventory buildup or wasted effort.
Why? If other processes produce faster than the constraint, it leads to inefficiency and excess stock.

✅ Step 4: Elevate the Constraint

Take actions to increase capacity of the constraint.
Examples:
- Buy another machine
- Hire or train more staff
- Work overtime
- Redesign workflows
Why? Once you’ve done everything possible with current resources, invest to solve the problem.

✅ Step 5: Repeat the Process

Once the current constraint is broken, a new one will appear.
Go back to Step 1 and identify the next bottleneck.
Why? Continuous improvement – always focus on what limits the system most.

Quick Summary: Action and Purpose (TOC Cycle)

1) Identify the constraint — Find the current bottleneck.
2) Exploit the constraint — Maximize use of existing capacity.
3) Subordinate everything else — Align all processes with the constraint.
4) Elevate the constraint — Increase its capacity.
5) Repeat the process — Improve continuously.

Key Differences from Traditional Costing

Traditional Costing vs Throughput Accounting (TA):
- Cost Focus: Traditional includes all costs (fixed + variable); TA focuses only on direct material as variable.
- Objective: Traditional aims to minimize total cost; TA aims to maximize throughput.
- Inventory Valuation: Traditional treats inventory as an asset; TA treats inventory as a liability (or waste) because it ties up working capital and often reflects unsynchronized production. Ideal inventory level = zero.
- Labor Treatment: Traditional—Direct Labour is a variable cost; TA—Direct Labour is treated as fixed (part of Total Factory Cost).
- Decision Basis: Traditional—Cost per unit; TA—Throughput per bottleneck hour/unit.
- Production Approach: Traditional—Produce to stock; TA—Produce to order.

Summary Points (Key Concepts of TA)

TOC focuses on maximizing throughput, not minimizing cost.
Identify and exploit bottlenecks to improve flow.
Only direct material is considered a variable cost in TA.
All other expenses = Operating Expenses (fixed in the short term).
Use Goldratt's 5-step method to manage constraints and improve system performance.

Core Concepts of Throughput Accounting (TA)

Concept 1: Cost Classification
- In TA, only Direct Material is considered a variable cost.
- All other costs—including Direct Labour, Overheads, and Indirect Materials—are grouped into a single block called:
  \text{Total Factory Cost}
- These are treated as fixed in the short run.
Concept 2: Inventory Viewpoint
- In Traditional Costing, inventory is an asset.
- In TA, inventory is a liability (or waste):
- Ties up working capital.
- Often reflects unsynchronized production.
- Production should only happen when there’s a customer order.
- Ideal inventory level = 0.
Concept 3: Throughput Focus
- Making money = Maximizing throughput.
- Throughput = Sales revenue – Direct material cost
- The bottleneck resource limits how fast throughput can be increased.
- So, managing the bottleneck is the key to increasing profit.

Traditional Costing vs TA (Summary Comparison)

Inventory: Asset (Traditional) vs Barrier/ liabilty (TA)
Cost Classification: Direct + Indirect costs (Trad) vs Direct Material only variable (TA)
Direct Labour: Variable (Trad) vs Fixed (TA)
Focus: Cost reduction (Trad) vs Maximizing throughput (TA)
Performance Measure: Cost per unit (Trad) vs Throughput per bottleneck hour (TA)
Production Approach: Produce to stock (Trad) vs Produce to order (TA)

TA in the Service Industry

Can TA be applied to services? Yes — TA is relevant in services, especially in multi-stage processes with limited resources.
Goal in service/not-for-profit settings: output efficiency — number of goal units served (e.g., patients, cases, clients).
Throughput in services = number of completed service units.

Example: Medical Screening Organization

Three sequential stages:
1) Take an X-ray: Time per patient = 0.50 hours; Total weekly hours = 80; Max patients = 80 ÷ 0.50 = 160
2) Interpret Result: Time per patient = 0.20 hours; Total weekly hours = 40; Max patients = 40 ÷ 0.20 = 200
3) Recall/Notify: Time per patient = 0.40 hours; Total weekly hours = 60; Max patients = 60 ÷ 0.40 = 150
Bottleneck is Stage 3 (Recall) since it yields the smallest max throughput: 150 patients/week.
Throughput = 150 patients/week.

Dealing with the Bottleneck (Stage 3)

Actions to improve throughput:
- Reduce Time Per Patient at Bottleneck
- Simplify or automate recall process
- Share or offload admin work
- Eliminate Idle Time
- Ensure recall team is fully utilized
- Avoid delays between stage 2 and 3
- Implement buffer scheduling to prevent interruptions
- Increase Bottleneck Capacity
- Add part-time staff for recall
- Extend working hours or shifts
- Reassign tasks from non-bottleneck areas

How is Production Priority Decided in TA?

When multiple products share a common bottleneck, prioritize the product that yields the highest throughput per unit of bottleneck resource.
Rule: Prioritize Product with Highest Throughput per Unit of Bottleneck Resource
Formula:
\text{Throughput per Unit of Bottleneck Resource} = \frac{\text{Selling Price} - \text{Direct Material Cost per unit}}{\text{Bottleneck Resource per Unit}}
Why this rule?
- The bottleneck limits total output, so produce items that generate the most money per unit of bottleneck time/capacity.
- Maximizes contribution earned from the most limited resource.

Example: Throughput per unit of bottleneck resource

Product A: Selling Price = ₹100, Direct Material Cost = ₹40, Bottleneck Resource per Unit = 2 hours
- Throughput per Unit = ₹100 - ₹40 = ₹60
- Throughput per bottleneck hour = 60 ÷ 2 = ₹30 per hour
Product B: Selling Price = ₹80, Direct Material Cost = ₹30, Bottleneck Resource per Unit = 1 hour
- Throughput per Unit = ₹50
- Throughput per bottleneck hour = 50 ÷ 1 = ₹50 per hour
Decision: Although A has higher selling price, B yields higher throughput per bottleneck hour and should be produced first.

Step-by-Step Production Priority Decision

1) Calculate throughput per unit = Selling Price − Direct Material.
2) Identify bottleneck resource usage per unit (e.g., machine hours, labor hours).
3) Compute Throughput per unit of bottleneck resource:
\text{Throughput per unit of bottleneck resource} = \frac{\text{Selling Price} - \text{Direct Material}}{\text{Bottleneck Resource per Unit}}
4) Rank products by the value from step 3 — higher value = higher priority.

Assumptions in This Approach

Bottleneck capacity is fixed in the short term.
Direct material is the only variable cost.
All other costs (labor, overheads) are fixed.
The goal is to maximize throughput, not reduce cost.

Summary Table: Elements of TA Priority and Focus

Bottleneck Resource: The most limited production factor.
Throughput per Unit: Sales − Direct Material per unit.
Priority Basis: Throughput per unit of bottleneck resource.
Objective: Maximize total throughput.
Decision Focus: Earn more per minute/hour/unit of bottleneck usage.

Throughput Accounting Ratio (TPAR) – A Key Performance Measurement

✅ What is TPAR? A financial ratio used in TA to evaluate how effectively a bottleneck resource is being used to generate throughput.

Formula:
\text{TPAR} = \frac{\text{Throughput per unit of bottleneck resource}}{\text{Factory cost per unit of bottleneck resource}}
Where:
- Throughput per unit of bottleneck resource = \frac{\text{Selling Price} - \text{Direct Material}}{\text{Units of bottleneck resource used}}
- Factory Cost per unit of bottleneck resource = \frac{\text{Total Factory Cost}}{\text{Total units of bottleneck resource available}}
Note: Factory cost = all operational expenses (fixed in short term).
Bottleneck resource = machine hours, labor hours, etc.

Interpretation of TPAR

TPAR Value | Interpretation
- \text{TPAR} > 1.0 → Good – Throughput exceeds factory cost, profitable.
- \text{TPAR} < 1.0 → Bad – Throughput is less than factory cost, loss.
Why TPAR matters:
1) Measures the efficiency of bottleneck usage.
2) Helps prioritize production (products with higher TPAR are more profitable).
3) Assists profitability decisions when multiple products compete for limited bottleneck capacity.
4) Helps decide whether to make or outsource.
5) Supports performance evaluation across departments or products.
TPAR vs. Throughput per Unit of Bottleneck Resource:
- Both give the same ranking for priority.
- However, TPAR shows profitability more clearly.

Quick Summary: How to Improve TPAR

Goal: Improve either the numerator (throughput per bottleneck unit) or reduce the denominator (factory cost per bottleneck unit).

1) Increase Throughput per Unit of Bottleneck Resource

How:
- (i) Increase Selling Price: Generates more revenue per unit.
- (ii) Reduce Material Cost per Unit: Increases contribution (throughput).
- (iii) Improve Efficiency: Use less bottleneck time per unit.
- (iv) Prioritize High TPAR Products: Focus on most profitable items.
- (v) Elevate the Bottleneck: Increase total capacity available.

2) Reduce Operating Cost per Unit of Bottleneck Resource

How:
- (i) Cut factory expenses: Lowers denominator of TPAR.
- (ii) Increase bottleneck hours available: Spreads fixed cost over more output.

Consequences of TPAR Improvement Measures

1) Increase selling price: May reduce customer demand.
2) Reduce material cost: May reduce product quality.
3) Cut operating/factory costs: May affect service quality, staff morale.
4) Improve efficiency: May require training or capital investment.
5) Elevate bottleneck: May need additional resources or overtime.

Important Notes

"Throughput" is sometimes also referred to as "Return" in TA.
Efficiency formula (time-based resources):
\text{Efficiency} (\%) = \frac{\text{Standard Hours}}{\text{Actual Hours}} \times 100

Summary Table: How to Improve TPAR (Conceptual View)

Increase Selling Price → Higher numerator but potential demand risk.
Reduce Material Cost → Higher numerator but potential quality risk.
Cut Operating Cost → Lower denominator but potential reliability/quality risk.
Improve Resource Efficiency → Higher throughput per bottleneck hour; may need training/capital.
Elevate the Bottleneck → Increases hours available but may require investment.

Final Notes

In TA, the focus is on the constraint and throughput rather than mere cost minimization.
Inventory should be minimized; aim for zero or near-zero inventory when feasible.
TA provides a framework to prioritize product mix and production scheduling under constraint conditions, across manufacturing and service contexts.
The TA toolkit includes the 5-step TOC cycle, the bottleneck-based priority rule, and the TPAR metric for performance evaluation.