The Cost of Technical Debt: What Are You Paying?

Estimate the Cost of Technical Debt

The cost of technical debt can be difficult to recognise because it rarely appears as a separate item in your technology budget. Instead, it shows up through development taking longer than expected, defects returning, maintenance becoming more expensive and business improvements being delayed.

For CEOs and business owners, the important question is not simply how much technical debt exists. It is how much that debt is costing the business, whether reducing it will produce a worthwhile return and what should happen before more money is committed.

Takeaways

What Is Technical Debt Really Costing You?

Technical debt is a way of describing software design or implementation choices that make future changes more difficult or expensive than they would otherwise be.

Sometimes developers knowingly accept a shortcut to release an important feature sooner. In other situations, technical debt develops gradually as requirements change, software grows or earlier design decisions become less suitable.

The problem is not necessarily the original decision.

Delivering a useful product sooner can be a sensible commercial choice, particularly when the business has a genuine opportunity or deadline.

The cost appears when the additional effort required to maintain or improve the software begins to outweigh the original benefit.

Understand the Interest on Technical Debt

Software expert Martin Fowler explains technical debt using a financial analogy.

The technical shortcuts or weaknesses represent the debt. The additional effort required to work with those limitations represents the interest.

Imagine a developer needs to add a new reporting function.

In a well-structured part of the application, the work might reasonably take three days.

However, the existing design requires the developer to modify several unrelated components, investigate undocumented behaviour and perform extra testing.

The task now takes five days.

Those additional two days are an example of the interest being paid on technical debt.

The figures are illustrative. Establishing the true difference between the actual effort and what would have been required in a better-designed system involves estimation and uncertainty.

Now consider that similar difficulties occur repeatedly across a development team.

The additional effort can consume capacity that could otherwise be used for customer improvements, operational efficiency or new business capabilities.

Debt Does Not Always Need Repaying

There is an important difference between technical debt existing and technical debt creating a meaningful business problem.

An older component might contain poorly structured code but rarely require changes.

Improving it could consume developer time without producing a worthwhile commercial benefit.

By comparison, technical debt in a frequently modified billing system might affect almost every new feature.

That debt deserves greater attention because the organisation keeps paying its associated costs.

I would concentrate on where the debt is affecting current operations or future business priorities, rather than attempting to remove every technical imperfection.

The goal is not perfect software. It is software that supports the business at a reasonable cost and level of risk.

Where Technical Debt Creates Hidden Costs

Technical debt can affect business expenditure in several ways.

Some consequences are relatively easy to measure. Others involve opportunities that are difficult to value precisely.

Understanding the distinction is essential when estimating the financial impact.

Slower Software Development

A common cost is the additional effort required to implement changes.

Developers may spend time understanding complicated code, working around poorly designed components or testing functions that should not be affected by the requested change.

A feature that would normally require two weeks might take three or four.

The additional work uses development capacity without necessarily providing additional business value.

However, slower delivery does not automatically prove technical debt is responsible.

Unclear requirements, changing priorities, missing skills, external dependencies and unrealistic estimates can produce similar symptoms.

The underlying cause needs to be investigated before assigning a financial cost to technical debt.

Repeated Defects and Rework

Poorly structured software can make it harder to change one function without affecting another.

The development team may fix a defect, only to discover that the change has introduced an unexpected problem elsewhere.

Additional investigation, testing and correction consume time.

Repeated defects can also affect customers and operational employees.

For example, an invoicing defect may require finance staff to investigate incorrect transactions and manually correct records.

The cost can extend beyond the development team.

It might include customer support, administration, financial reconciliation and management attention.

These costs should be recorded separately where possible, while avoiding counting the same work twice.

Increasing Maintenance Effort

Some maintenance is normal and necessary.

Applications require security updates, software dependency upgrades, infrastructure changes and adjustments to external integrations.

Technical debt becomes relevant when the system’s design makes those activities unnecessarily difficult.

For example, upgrading an external service might require extensive changes because integration details are duplicated throughout the application.

The business pays for additional development effort simply to maintain an existing capability.

This is particularly relevant when an application depends on critical operational processes.

The organisation may be spending more each year to maintain functionality that has not materially improved.

Delayed Business Improvements

Technical debt can also create opportunity costs.

Imagine an established subscription business planning to introduce a new pricing model.

The commercial team has identified a customer opportunity, but the development team explains that modifying the existing billing logic will require substantial additional work.

The launch is delayed.

The business may lose some potential revenue or continue operating with an inefficient pricing structure.

Those consequences matter, but they are not always straightforward to measure.

A projected revenue opportunity is not the same as confirmed financial loss.

I recommend separating measurable development expenditure from estimated business opportunities, with assumptions clearly documented.

How to Estimate Technical Debt Costs

A practical technical debt cost assessment does not require the CEO to understand every detail of the source code.

It requires the development team to identify specific problems, explain their consequences and provide evidence of the additional effort involved.

I would start with a small number of important examples rather than attempting to calculate a single figure for the entire application.

Identify Specific Sources of Debt

Ask the technical team to identify the components or design problems that are creating recurring difficulties.

These might include:

• Closely connected software components that make changes difficult.
• Duplicated business rules that must be updated in several places.
• Poorly structured database queries affecting important operations.
• Missing automated tests that increase regression testing effort.
• Outdated dependencies that complicate upgrades.
• Architecture limitations that create repeated workarounds.

Each item should describe the affected business process and explain why the existing approach creates additional work.

The Carnegie Mellon Software Engineering Institute recommends identifying technical debt items, documenting their consequences and evaluating their lifecycle costs.

That is a useful approach because it turns a broad technical concern into a collection of specific problems that management can assess.

Estimate the Additional Effort

For each item, examine recent development work where the problem affected delivery.

Ask how much additional effort was required and why.

Evidence might come from completed development tasks, defect records, support tickets, release history or discussions with the developers who performed the work.

Where records are incomplete, use clearly labelled estimates.

Martin Fowler’s estimated-interest approach compares actual development effort with an estimate of the effort that would have been required without the technical limitation.

This is useful, but the comparison is inherently uncertain.

You cannot observe the same development task being completed simultaneously in the existing system and an imaginary improved version.

The objective is a credible range that supports a business decision, not a falsely precise figure.

Use a Simple Cost Register

A technical debt cost register can connect each problem with the evidence and commercial consequences.

Technical debt issue	Evidence	Business impact	Cost estimate
Complicated billing logic	Extra changes across modules	Slower billing enhancements	Additional developer hours
Unreliable automated tests	Repeated manual regression testing	Longer release preparation	Testing effort per release
Poor database performance	Investigation and support records	Operational delays	Support effort and validated business impact
Outdated dependencies	Upgrade failures and workarounds	More difficult maintenance	Additional upgrade effort
Closely coupled components	Unintended defects following changes	Rework and delivery disruption	Defect correction effort

Use the register to record estimates, assumptions, evidence, responsible owners and the frequency of the problem.

Do not automatically total every possible consequence.

For example, if additional developer hours have already been counted as rework, counting those same hours again under slower delivery would overstate the cost.

Translate Time Into Money

Once the additional effort has been estimated, apply an appropriate development cost rate.

A simple calculation is:

Annual technical debt effort cost = Additional hours attributable to technical debt × Relevant hourly delivery cost

The hourly cost should reflect the decision being made.

For an external development supplier, an appropriate contracted hourly rate may be useful.

For an internal team, an estimate could include salary, employment on-costs and relevant overheads.

The organisation should distinguish the cost of internal capacity from cash expenditure that could actually be avoided.

That distinction becomes particularly important when evaluating whether remediation will produce financial savings.

An Example of Technical Debt Costs

Consider a hypothetical Australian business operating a custom customer management and billing platform.

The company employs four software developers who maintain the application and deliver improvements.

Management is concerned that development seems to be taking longer while the volume of completed work is falling.

The technical team believes accumulated technical debt is contributing to the problem.

Rather than accepting a broad claim, the business examines completed work and estimates the additional effort associated with several recurring technical limitations.

Calculate the Development Impact

For this illustrative example, assume:

Measure	Assumption
Number of developers	4
Productive development hours per developer annually	1,600
Total annual development capacity	6,400 hours
Estimated capacity consumed by technical debt	15%
Additional effort attributable to technical debt	960 hours
Blended internal delivery cost	$120/hour
Estimated annual capacity cost	$115,200

All figures are hypothetical and are not industry averages.

The calculation is:

6,400 hours × 15% × $120 = $115,200 per year

That means the business is estimating that technical debt consumes development capacity equivalent to approximately $115,200 annually.

It does not mean the business can automatically recover $115,200 in cash by fixing the software.

If the team remains employed, salaries will generally continue being paid.

The potential benefit is that developers may have more time available for productive work.

Whether that capacity becomes additional revenue, faster delivery or reduced external expenditure depends on how the business uses it.

Assess a Proposed Improvement

Suppose the development team recommends restructuring the most troublesome billing components and introducing better automated tests.

The estimated remediation effort is 300 hours.

At the same blended cost rate:

300 hours × $120 = $36,000

The team believes these improvements could eliminate 360 hours of recurring technical debt effort annually.

The potential annual capacity benefit would be:

360 hours × $120 = $43,200

On those assumptions, the remediation cost is equivalent to approximately ten months of the estimated annual capacity benefit.

However, the improvement must actually deliver the expected reduction in effort.

It is also possible that new requirements, other technical constraints or implementation difficulties will affect the outcome.

The calculation is a starting point for evaluating the investment, not proof that the proposed work will pay for itself.

Separate Capacity From Cash Savings

A CFO should distinguish three outcomes:

Direct cash savings: Expenditure genuinely avoided, such as reduced external development invoices or lower support costs.

Recovered development capacity: Time that existing employees can redirect towards other valuable work.

Business opportunity: Potential gains from releasing improvements sooner or reducing delays affecting customers and operations.

These outcomes should not be treated as interchangeable.

For example, recovered development capacity is valuable when the business has important work waiting to be delivered.

If there is no useful work available, the financial benefit may be much smaller.

Similarly, bringing a planned feature forward may create business value, but that value needs its own assumptions and evidence.

The strongest business cases distinguish these categories rather than presenting one impressive total.

Not Every Software Problem Is Technical Debt

One of the biggest risks in estimating technical debt costs is attributing every development problem to the code.

That can produce misleading estimates and expensive recommendations.

A development project may be running late because requirements keep changing, stakeholders cannot agree on priorities or a supplier lacks the necessary experience.

Those problems can exist even when the software is reasonably maintainable.

Distinguish Debt From Poor Delivery

Consider a team that repeatedly misses its delivery commitments.

The supplier explains that technical debt makes estimates unreliable.

That might be correct.

However, the business should also examine whether requirements were understood, priorities remained stable and the estimates were realistic.

Other possible causes include:

• Too much work being undertaken simultaneously.
• Poor communication between developers and business stakeholders.
• Delays obtaining decisions or approvals.
• Inadequate developer experience.
• Frequent interruptions or changing requirements.
• Weak testing and release practices unrelated to the claimed debt.

Some of these factors can interact with technical debt.

The important point is that management needs to understand the underlying causes before approving remediation expenditure.

An independent Software Development Review may help where the causes of rising costs or delivery delays remain unclear.

Treat Tool Estimates Carefully

Automated code analysis tools can identify maintainability concerns and estimate the effort required to correct certain issues.

For example, SonarQube’s technical debt metrics include estimates of the effort required to address identified maintainability problems.

These measures can be valuable for technical teams.

However, an automated remediation estimate is not a direct measurement of the financial impact on your business.

A tool might identify hundreds of hours of potential improvements in code that is rarely modified.

Another component might have a smaller estimated remediation effort but affect nearly every customer transaction.

The commercial significance is different.

Use technical analysis to understand the software’s condition, then combine it with actual development evidence and business priorities.

Decide Which Debt Is Worth Fixing

Once the organisation has identified the main sources of technical debt and their likely costs, the next question is which problems deserve investment.

Not every problem requires immediate remediation.

I would assess each proposed improvement against its expected business value, cost, operational risk and relevance to future development.

Compare Cost and Benefit

A useful assessment considers:

• The additional effort currently caused by the debt.
• How frequently the affected software needs to change.
• The proposed cost of remediation.
• The likelihood of reducing future effort.
• The operational risks introduced or reduced.
• The effect on planned business initiatives.
• The uncertainty surrounding the estimates.

The business should also consider whether leaving the problem unresolved creates an unacceptable risk, even when the financial return is difficult to calculate.

For example, a weakness affecting recovery of a critical application may justify investment because of the consequences of prolonged service disruption.

That decision should be based on an explicit assessment of risk rather than a simple payback calculation.

Use a Remediation Decision Matrix

Business situation	Recommended approach
High recurring cost and manageable repair	Prioritise remediation
High operational risk	Investigate urgently and apply appropriate controls
Low cost and infrequent changes	Consider accepting the debt
Uncertain impact or expensive repair	Gather more evidence
Problems concentrated in one component	Consider targeted refactoring
Proposed full rebuild	Require a wider cost, risk and options assessment

The matrix is a decision aid, not an automatic approval process.

A technically appealing improvement may still compete with more valuable business investments.

Conversely, a relatively small technical change may be worthwhile if it removes a recurring delivery constraint.

Consider the Cost of Doing Nothing

Choosing not to fix technical debt can be a sensible business decision.

It should still be deliberate.

Management needs to understand whether the additional costs will remain stable, increase as the software changes or create greater operational exposure.

An application approaching retirement may not justify extensive structural improvements.

A platform expected to support substantial growth may require more attention to maintainability.

The decision should reflect how the business intends to use the technology.

Build a Practical Remediation Business Case

A good remediation proposal should connect the technical improvement to a business outcome.

The development team should not need to produce a complex financial model for every minor code improvement.

However, larger requests for additional funding deserve a clear explanation.

Ask Five Business Questions

Before approving a significant remediation initiative, I would ask:

1. What is the problem? Identify the specific technical limitation and affected business functions.
2. What is it costing us? Describe recurring effort, direct expenditure, operational risk and lost opportunities separately.
3. What are we proposing? Explain the changes required and the estimated remediation cost.
4. What will improve? Describe expected improvements in delivery effort, stability, risk or business capability.
5. How will we verify the benefit? Establish what will be measured after the work is completed.

The fifth question is particularly important.

Without a way to evaluate the outcome, the business may spend money reducing technical debt without establishing whether the investment achieved its purpose.

Consider a Limited Trial

When the expected benefit is uncertain, a small, controlled improvement can provide useful evidence.

For example, the development team might refactor a frequently modified component and measure how the effort required for similar changes evolves.

A suitable trial should have clear boundaries, realistic testing and a defined evaluation point.

The objective is to learn whether the proposed approach works before committing to a much larger initiative.

It should not disrupt important business operations simply to prove a technical theory.

Avoid the Automatic Rebuild

Sometimes technical debt leads to recommendations for a complete software rebuild.

That may be justified when the existing system has fundamental limitations that cannot reasonably be corrected.

However, rebuilding introduces its own expenditure, delivery uncertainty, data migration needs and operational risks.

A full rebuild should be considered alongside targeted repairs, incremental replacement and continued maintenance.

I would want to understand why less disruptive options are unsuitable before recommending replacement.

An independent Technology Strategy engagement may be appropriate where the decision forms part of a wider technology investment or modernisation programme.

Make Technical Debt Visible to Leadership

Technical debt is easier to manage when developers and business leaders share an understanding of its consequences.

Executives do not need detailed reports about every code quality warning.

They need visibility of the problems materially affecting delivery, expenditure and risk.

Report Commercial Consequences

A useful management report might identify the most important technical debt items and show:

• The affected business capability.
• The evidence supporting the concern.
• Estimated additional effort or cost.
• Operational consequences.
• Proposed action and expenditure.
• Responsible decision-maker.
• Current status and next review date.

The report should help management make decisions.

A long register of technical issues can be useful to developers, but it should not become another document that consumes time without changing priorities.

Balance Features and Improvements

Development teams often face pressure to deliver new functionality while maintaining existing software.

Technical debt remediation competes with that work for the same development capacity.

I do not favour automatically assigning a fixed percentage of every development budget to technical debt.

The right allocation depends on the condition of the system, the business roadmap and the consequences of leaving particular issues unresolved.

An urgent operational problem may deserve immediate attention.

A minor maintainability concern may reasonably wait until the affected code is next modified.

What matters is that priorities are understood and the trade-offs are explicit.

This is where effective Project Delivery oversight can help connect technical work with business priorities, available capacity and delivery expectations.

Review the Results

After completing important remediation work, assess whether the expected improvements occurred.

Compare relevant development activities before and after the changes, taking account of differences in complexity and requirements.

Look for improvements such as reduced repeat defects, less time spent on known workarounds or easier maintenance of frequently changed components.

Avoid claiming that every improvement was caused by remediation alone.

Team experience, better requirements and changing workloads can also affect results.

The review should identify what has improved, what remains uncertain and whether further investment is justified.

When Independent Assessment Makes Sense

Your existing development team may be entirely capable of identifying, estimating and addressing technical debt.

An independent review becomes more valuable when management cannot confidently assess the claims being made or the proposed investment is commercially substantial.

Consider independent advice when:

• Development costs are increasing without clear explanations.
• Technical debt is repeatedly blamed for missed commitments.
• A supplier recommends extensive remediation or rebuilding.
• Different developers disagree about the seriousness of technical problems.
• Management lacks reliable evidence of the expected benefits.
• Significant expenditure depends on accepting a supplier’s assessment.

My approach is to understand the business problem first, then examine the technical evidence and the people involved.

The existing developers may have valid concerns. Equally, the business may be experiencing delivery problems that technical improvements alone will not resolve.

The objective is to establish what matters commercially and recommend a proportionate response.

If technical debt continues to compete with strategic priorities, the organisation may benefit from ongoing Fractional CTO support to help guide investment decisions and technical direction.

That is not necessary for every business. Sometimes a focused assessment and a clear improvement plan are enough.

Frequently Asked Questions

How Do You Calculate Technical Debt?

Estimate the additional effort caused by specific technical limitations, then apply an appropriate development cost rate. Separate measurable expenditure from recovered capacity, operational risk and uncertain business opportunities.

How Much Does Technical Debt Cost?

The cost of technical debt varies with the software, its condition and how frequently affected components are changed. A credible estimate should use evidence from the organisation rather than an assumed industry-wide percentage.

Is Technical Debt Always Bad?

No. Some technical compromises are commercially reasonable when they deliver value sooner and their future consequences remain manageable. The important issue is whether the ongoing cost or risk justifies remediation.

Should We Fix All Technical Debt?

Usually not. Prioritise issues according to their business impact, recurring cost, operational risk and relevance to planned work. Some debt can reasonably remain unresolved.

When Is a Technical Debt Review Worth It?

An independent review is useful when technical debt is affecting important business decisions, development expenditure is increasing or management needs confidence before approving substantial remediation or replacement work.

Conclusion

Technical debt deserves management attention when its ongoing costs or risks begin to affect important business outcomes. If your development team is recommending substantial remediation, my independent Software Development Review can help examine the evidence, assess the business consequences and clarify your options before committing more money. Better technology investment decisions start with understanding the real cost of technical debt.