Software Maintenance Costs: What You Will Really Pay After Launch

Software maintenance costs explained: what each type covers, what pushes the bill up, how to budget bottom-up and what a good support agreement includes.

10 November 202610 min read

Software engineer holding a mug at a desk with two monitors, illustrating software maintenance costs after launch

Software maintenance costs are the recurring spend that keeps a system working after launch: fixing faults, applying security patches, adapting to new phones, browsers and third-party services, paying for hosting and monitoring, and making small improvements. They do not stop when the build ends.

No single percentage fits every system. The sound approach is to price the work bottom-up, from the parts your software depends on, and to agree the support model before you sign the build contract.

Key Takeaways

Maintenance covers four kinds of work: fixing faults, adapting to a changing environment, improving the product and preventing future faults. Each one has a different cost pattern.
The number of integrations, the age of the technology and the rules you operate under drive the bill more than the original build price does.
The popular "15 to 20 per cent of build cost a year" figure is widely repeated but thinly sourced, so treat it as a sanity check, not a budget.
A bottom-up estimate lists hosting, patching, monitoring, support hours and a small improvement allowance as separate lines.
A good support agreement names response times, what is in and out of scope, handover documentation and how you can leave.

What Do Software Maintenance Costs Actually Cover?

The international standard for software maintenance, ISO/IEC/IEEE 14764:2022, splits maintenance into four types. Each type shows up as a different line on your invoice.

Corrective: fixing what is broken

This is repairing faults found after delivery so the software meets its agreed requirements. Real customers find problems that testing missed, so the first months after launch usually need the most attention. A fair vendor separates defects in the original work, which a warranty period should cover, from new requests.

Adaptive: keeping up with things you do not control

The standard describes this as keeping software usable in a changed environment. In practice it means new iOS and Android releases, browser changes, payment provider updates, expiring certificates and changes to any service you connect to. You cannot schedule this work, which is why integration-heavy systems cost more to keep running.

Perfective and preventive: improving and de-risking

Perfective work improves performance or usability. Preventive work fixes hidden faults before they appear in the live system, such as replacing a library that is about to lose support.

What Pushes Software Maintenance Costs Up?

Maintenance effort follows the number of moving parts and how often outside services change them. Two systems built for the same price can cost very different amounts to run. These are the drivers we ask about first.

Dependencies. Most software is assembled from open-source and commercial components that release updates on their own timetable. Each update needs testing. Wikipedia's overview of software maintenance notes that testing to confirm existing features still work often makes up most of the maintenance cost.
Security patching. The Australian Cyber Security Centre's Essential Eight maturity model sets patching timeframes, for example fixes within 48 hours for online services when a vulnerability is rated critical by the vendor or a working exploit exists.
Hosting, monitoring and backups. Cloud hosting, databases, email delivery and third-party services usually charge monthly, and the bill grows with usage. They belong in the maintenance budget, not the build budget.
Small enhancements. Every live system attracts requests. Without a set allowance, each one becomes a negotiation.
Regulation. Handling personal or financial data adds review and audit work.

How does technical debt change the bill?

Technical debt is the future cost created when a team chooses a quick solution over a sound one. It behaves like interest: every later change takes longer because the shortcuts are still in the way. Systems rushed to launch, or stretched by late changes, cost more to maintain, which is one reason we keep a firm line on scope. Our post on software project scope creep shows how unpriced changes quietly build that debt.

How Much Should You Budget for Software Maintenance Each Year?

Search for the answer and you will find the same figure repeated: 15 to 20 per cent of the build cost every year. It is easy to remember. The trouble is the evidence behind it.

Why the percentage rule is only a starting point

A Berlin software agency, happycoding, reviewed the topic in 2026 and called the 15 to 20 per cent figure handed on from page to page and almost never backed by a source. The same article cites a 2021 meta-analysis by Franz Lehner at the University of Passau, covering 30 publications over four decades. It reportedly judged the often-quoted 60 to 70 per cent maintenance share of annual software costs too high, but put 30 to 40 per cent as realistic. That is a different measure from a percentage of build cost, and we have only read it second-hand, so treat it as a sign the range is wide.

A flat percentage also cannot see that costs run higher in the first months, or that they climb with every integration or compliance duty.

A bottom-up estimate you can check

List each cost as its own line, then add them. The figures below are invented to show the method and are not benchmarks. All amounts are AUD.

Hosting and services - How to estimate it: Add the real monthly bills, then allow for growth; Illustration only: $600 a month, so $7,200 a year
Patching and updates - How to estimate it: Hours per month for dependency, OS and browser updates, plus testing; Illustration only: 12 hours a month at $160, so $23,040
Monitoring and support - How to estimate it: Expected tickets multiplied by average handling time; Illustration only: 6 hours a month at $160, so $11,520
Small enhancements - How to estimate it: A fixed allowance the business can spend on requests; Illustration only: $15,000
Contingency - How to estimate it: Extra for the unscheduled adaptive work; Illustration only: 10 to 15 per cent of the above

Ask your vendor to fill in this table with their own rates. A single round number with no working cannot be compared with anyone else's quote.

Retainer, Time-and-Materials or Fixed Support: Which Fits?

Each model moves risk differently. Choose by how predictable your system's demands are, not by the lowest headline price.

Monthly retainer. You pay for a set block of hours or a defined service level. Costs are predictable and the team stays familiar with your system. The risk is paying for unused hours, so check whether they roll over.
Time and materials. You pay for hours worked. It suits low-volume, stable systems. The risk is a variable bill, so ask for a monthly cap and reporting.
Fixed-scope support. A set price for a defined list of tasks, such as quarterly patching and a security check. Anything outside the list is quoted separately, so the list needs to be precise.

Many businesses blend them: a small retainer for patching and monitoring, with time and materials for larger improvements. The same thinking applies to industry business systems, where uptime and integrations matter most.

What Should a Good Support Agreement Include?

Ongoing software support is won or lost in the agreement. Look for these points in writing.

Response and resolution times. Separate targets by severity, with support hours and how time is measured.
Scope in and out. State what counts as a defect, what counts as a change request and who decides.
Patching schedule. How often updates are applied, how fast critical security fixes are released and how you are told.
Reporting. A short monthly summary of tickets, hours, incidents and upcoming risks.
Handover documentation. Architecture notes, environment details, release steps and access lists kept current, so a new team could take over.
Exit terms. Notice period, data return, code and credential ownership, and help with transition. Fair terms let you leave without penalty.

Related Resources

Common Questions About Software Maintenance Costs

1. How much does software maintenance cost per year?

A common starting point is 15 to 20 per cent of build cost, but the sourcing is weak and real costs vary widely. Build a bottom-up estimate from hosting, patching, support hours and an improvement allowance instead.

2. What is included in software maintenance?

Four types of work: corrective (fixing faults), adaptive (keeping up with changes to phones, browsers and connected services), perfective (improvements) and preventive (fixing latent faults early). Hosting and monitoring usually sit alongside as running costs.

3. Is a maintenance retainer worth it?

Usually, if your software is customer-facing or connected to other systems. A retainer keeps a team familiar with your code and gives you predictable costs. For a small, stable internal tool, time and materials can be cheaper.

4. Why does old software cost more to maintain?

Older systems carry technical debt and depend on components that are no longer supported, so each change takes longer and carries more risk.

5. Can I move maintenance to a different vendor?

Yes, if you own the code and accounts and the documentation is current. Write these rights into the agreement from the start so a switch is a handover, not a rescue.

Budget for Maintenance Before You Build

The build is the most visible part of what software costs. The rest is fixes, patches, hosting, small improvements and the debt you carry, and it is far easier to plan for in the first quote than to find after launch.

Ask any vendor for the support model, the bottom-up estimate and the exit terms alongside the build price. If you are weighing a new system or taking over an existing one, send 9Byte a brief and we will respond with the build scope and a maintenance plan priced side by side.