What does custom software maintenance cost each year?

Straight answer up front. Then the details.

The short answer

There is no honest universal number, and no universal percentage. A simple internal tool with one integration and a mission-critical system with six integrations do not share a maintenance profile, and quoting a single figure for both would be a sales tactic rather than an answer.

What you can know before you build is the structure: six distinct cost categories, of which only some are truly unavoidable. Infrastructure and security upkeep are ongoing by nature. New feature work is a choice you make later. Confusing those two is why maintenance quotes feel unpredictable.

Why the percentage rule of thumb doesn’t survive contact

You’ll see figures like “15–20% of development cost per year” repeated widely online. They’re usually recycled from enterprise IT contexts with staffing models and compliance obligations that have nothing to do with a 12-person contracting business. We’re not going to adopt a number we can’t defend for your system.

The more useful framing: maintenance cost is driven by complexity, integration count, business criticality, change frequency and external dependencies. Two systems that cost the same to build can differ several-fold in what they cost to keep healthy.

The lifecycle cost stack

Six categories. Ask any builder to quote against these separately rather than as a single monthly number — a bundled figure hides which parts you actually control.

1. Infrastructure

The floor. Unavoidable, generally the most predictable, and it should be visible on your own accounts.

HostingWhere the application runs. Scales with usage and how much redundancy the business needs.
Database and storageWhere records, documents and photos live. Grows steadily with years of job history.
Email and SMSNotifications and customer messaging — usually priced per message or per volume tier.
Third-party APIsAccounting, payments, mapping, and anything else the system connects to. Each has its own terms.
Monitoring and domainsUptime checks, error tracking, domain registration and certificates. Small individually, real in total.

2. Corrective maintenance

Fixing what's genuinely broken. Highest in the first months after launch, then it should fall — and if it doesn't, that's a signal.

BugsDefects surfacing under real-world use that testing didn't reach. Expect some; expect them to taper.
FailuresSomething stops working — a job, a queue, a scheduled process. Usually urgent by definition.
Broken integrationsA third party changed something. Not your fault, still your problem, and the most common recurring category.
Unexpected behaviorIt works as built but not as the business needed. Often really a discovery gap, not a defect.

3. Security and dependency maintenance

The category most often skipped and most expensive to skip. Software decays when it isn't updated, whether or not anyone is using it.

Dependency updatesThe components underneath your system release new versions. Falling far behind makes future work harder and riskier.
Security patchesPublished vulnerabilities in components you rely on. Applied on their schedule, not yours.
Credential rotationAPI keys and access credentials expire or need rotating — a leading cause of quiet integration failure.
Platform changesHosting providers and API vendors deprecate things. Sometimes with notice, sometimes with a deadline.

4. Operational support

People, not code. Heaviest right after launch and after any staffing change.

Questions'How do I…' from the office and the field. Good documentation reduces this significantly over time.
Permissions and user changesOnboarding, offboarding and role changes. Often something you can handle in-house with admin access.
Data correctionsSomeone entered a job wrong months ago. Some fixes are self-service; some need a developer.
TrainingNew hires, and refreshers when a workflow changes. Recurring in any business with turnover.

5. Monitoring and reliability

What turns a silent failure into a notification. Cheap relative to what it prevents.

AlertsSomething watches the system and tells a person when it breaks — before a customer does.
LogsThe record of what happened, which is what makes diagnosis fast rather than speculative.
BackupsAutomatic, retained, and stored somewhere separate from the system they protect.
Recovery checksPeriodically proving a restore actually works. An untested backup is an assumption, not a backup.

6. Feature work

NOT maintenance. This is investment in new capability, and treating it as upkeep is how 'maintenance cost' quietly balloons.

New workflowsThe business changed — a new service line, a new process. You chose this; it should be scoped and priced as a project.
New reportsNew questions you want the system to answer as the operation matures.
New integrationsConnecting a tool you've adopted since launch.
New automationRemoving manual steps that have proven repetitive in real use.

Categories 1 through 5 keep an existing system healthy. Category 6 makes it do more. Any quote that blends them together makes it impossible to tell whether you’re paying to keep the lights on or to build something new — insist they’re separated.

What actually drives the number

Rather than invent dollar figures, here’s what moves the effort. Place your own situation against these three shapes.

Lightest lifecycle burden

Low-change internal tool

One or two workflows, few or no external integrations
Modest hosting, small user group, changes rarely requested
Dominated by infrastructure and periodic dependency updates
Corrective work tapers to near-zero once it has settled

The common contractor case

Moderate integration system

Several workflows, accounting integration, field and office users
Integrations are the recurring source of corrective work
Support demand spikes after launch, then flattens as habits form
Feature requests arrive steadily as the business finds new uses

Heaviest — and deliberately so

Mission-critical, multi-integration

The business genuinely stops if it stops; downtime has a price per hour
Multiple external dependencies, each with its own change schedule
Justifies real monitoring, tested recovery and faster response expectations
Security and dependency upkeep become non-negotiable, not optional

Complexity, integration count, business criticality, change frequency, security exposure and external dependencies drive lifecycle cost far more than the size of the original build. That’s also an argument for the smallest useful system: less surface area to maintain forever.

Where we stand on support

We don’t think you should have to pay a mandatory retainer simply to keep access to a system built for your business. Access to what’s yours shouldn’t be a subscription.

That is not the same as claiming maintenance is free — it isn’t, and anyone implying otherwise is hiding a cost. Hosting runs monthly. Third-party services bill. Dependencies need updating. Support takes real hours. What we think you should get is the choice of how that’s handled, and cost you can see.

Support structures worth discussing before a build (not a published ACS price list):

Self-managed — you hold the accounts and handle day-to-day administration yourself
Hourly support — you call when you need help, and pay for what you use
Project-based changes — new capability scoped and priced as its own piece of work
Optional monthly support — a defined scope and response expectation, if you want one

Which of these fits depends on the system, your team and the agreement. Get the specifics in writing before a build starts rather than after — and read “build it once and you’re done” as a warning sign wherever you see it.

ACS guidance — written from operator experience building systems for contractors, not from vendor marketing. Last reviewed August 10, 2026.

Reviewed by Connor Adler, Adler Custom Systems

Cost categories reflect how ACS structures and discusses lifecycle work. No universal maintenance percentage is adopted or implied, and no dollar figures are published because they would be unsupported. Support structures listed are possible arrangements to discuss, not a committed ACS price list or contractual offer.

Our approach

We design systems around your business.

Built from inside the operation—not from the sidelines. The people doing the work help shape the system.

Listen
Map
Build
Test
Refine

Worked with Connor

He Helped Me Believe

Robert shares how working with Connor helped him believe in himself, gain clarity around his purpose and begin turning his mission into something real.

Watch Robert’s story

Where to go from here

Scope support

Support cost follows system complexity, and complexity follows your workflow. The audit maps how your operation actually runs — the honest starting point for what a system would cost to keep healthy.

Scope Support

About two minutes
No sales call required