The short answer
Custom software typically costs 15 to 20 percent of the build cost per year to maintain, which for small-business projects built for $3,000 to $40,000 is $450 to $8,000 annually. That percentage pays for people's time: security updates, keeping up with the services your software talks to, fixing what users find, and small improvements. Hosting and monitoring are separate running costs.
None of that is a fee for nothing. Software sits on a language, a database, and open-source libraries, all of which keep moving whether or not anyone changes a line of your code. This post covers the four cost buckets, three example builds, and when to rebuild instead.
The four buckets maintenance money goes into
Two buckets are monthly running costs. The other two are hours, and the hours are what the 15–20% pays for.
1. Hosting
Hosting is where the software runs: the server, the database, and their backups. Our cost guide puts it at $20–$200 per month for most small-business apps, and that's the number to use from the $5,000–$15,000 band up. For builds under $5,000, plan on roughly $5–$50 a month. That covers a small managed setup: at Heroku, a Basic dyno is $7 a month and an Essential-0 Postgres database is $5.
2. Monitoring
Monitoring means uptime checks and error tracking: the alerts that tell you about a failure before a customer does. Pythn sets it up in the Launch & Support stage, so we (and you) know if something breaks. Sentry, an error-tracking service, has a free Developer plan for one user and a Team plan at $26 a month billed annually. A free tier or one paid plan like that keeps this bucket at $0–$30 a month.
3. Updates
This is the easy bucket to forget, because nothing visibly changes. Python releases are supported for five years: Python 3.10, released in October 2021, reaches end of life in October 2026. PostgreSQL supports each major version for five years; version 14 is scheduled for its final release on November 12, 2026. Software built on those two versions in late 2021 is due for upgrades this fall, new features or not.
The CA/Browser Forum, where certificate issuers and browser makers set the baseline requirements for HTTPS certificates, voted to cut their maximum lifetime from 398 days to 47 in steps between March 2026 and March 2029, so renewal has to be automated, not remembered. And as our automation page puts it, APIs change. Taken every quarter, each round of updates is small; left for four years, it's a project.
4. Bug fixes and small improvements
Real users find the paths nobody tested. Pythn's 30 days of included post-launch support is there to catch the issues that only surface once real users hit the system, but fixes don't stop on day 31: a vendor renames a field, the business adds a step. This bucket also covers active improvements: small requests like “can the report show last month too?”
Where 15 to 20 percent comes from
We won't dress it up as an industry benchmark. It's the planning rule Pythn uses and the figure in our cost guide: usually 15–20% of the build cost per year if you want active improvements and fast response to issues.
It scales with the build for a plain reason: a bigger build has more screens, integrations, and libraries, so more to update and more places for bugs to surface.
It also helps to turn the percentage into time. At the $100–$180 an hour the cost guide lists for a senior freelancer or small shop, the $1,800–$2,400 a year for the $12,000 tool below buys 10 to 24 hours, or two and a half to six hours a quarter. Not a full-time job, and not zero.
Three scenarios with real numbers
Here's the rule applied to three builds from three price bands. They're illustrations, not quotes: updates and bug fixes are 15–20% of the build price, hosting uses the ranges above, and monitoring is $0–$30 a month.
A $3,000 marketing site
A polished marketing site with custom design, a small CMS, and a blog.
- Updates and bug fixes: 15–20% of $3,000 = $450–$600 a year.
- Hosting: $5–$50 a month, or $60–$600 a year.
- Monitoring: $0–$360 a year.
All in: $510–$1,560 a year. At this size, hosting can cost as much as the maintenance itself.
A $12,000 internal tool
A focused internal tool, such as a scheduling tool with logins that replaces a shared spreadsheet.
- Updates and bug fixes: 15–20% of $12,000 = $1,800–$2,400 a year.
- Hosting: $20–$200 a month, or $240–$2,400 a year.
- Monitoring: $0–$360 a year.
All in: $2,040–$5,160 a year. The maintenance line is the 10–24 hours a year worked out above: quarterly updates, a look at the error log, and fixes for what users report.
A $40,000 business platform
A full business platform with authentication, admin controls, a real data model, and two to five integrations.
- Updates and bug fixes: 15–20% of $40,000 = $6,000–$8,000 a year.
- Hosting: $20–$200 a month, or $240–$2,400 a year.
- Monitoring: $0–$360 a year.
All in: $6,240–$10,760 a year. People's time dominates here: two to five integrations means two to five vendors changing things on their own schedule, and keeping up with them comes out of this budget.
Across the three, the maintenance line alone runs $450–$8,000 a year: the range in the short answer.
How to budget for maintenance
- Count it before you sign. When you weigh a build against a subscription, add 15–20% a year to the build side, as our custom vs SaaS framework does.
- Ask about the maintenance model up front. It belongs on your list of questions to ask before hiring a developer, alongside who owns the code.
- Pick a support model on purpose. A retainer suits a tool that runs daily operations; on-demand help suits a site that rarely changes.
- List the running costs. Hosting, monitoring, the domain, and third-party services such as payment processing, email, or SMS each bill somewhere. Know where, and whose name is on the account.
Not sure what the build will cost? The cost calculator gives you a band; apply 15–20% and you have a first maintenance budget.
When to stop maintaining and rebuild
Maintain for as long as the software fits the business and its foundations can be upgraded in reasonable steps. Price a re-platform when you see these signs:
- The foundations are out of support, and upgrading them means touching most of the code.
- Maintenance runs well past 15–20% year after year, because every fix breaks something else.
- The business has changed shape, and the data model no longer fits how you work.
- An off-the-shelf product now covers the workflow. Run the custom vs SaaS quiz; the answer can change as your business does.
A re-platform is a new build, priced like one: discovery call, written design document, fixed price. Before pricing a rewrite of everything, ask whether rebuilding the worst part would do.
Frequently asked questions
How much does custom software cost to maintain?
Plan on 15–20% of the build cost per year for updates, bug fixes, and small improvements. That's $450–$600 a year for a $3,000 marketing site, $1,800–$2,400 for a $12,000 internal tool, and $6,000–$8,000 for a $40,000 platform, with hosting and monitoring on top.
What happens when my developer goes out of business?
If you hold the pieces, you hire someone else and carry on. Before you need them, make sure your company has three things: the source code; admin access to the hosting, the domain registrar, the database, and every connected service; and the documentation, such as the design document and a deployment runbook. A new developer then starts by learning the code, not recovering access to it. At Pythn, clients own the code, domain, and data from day one, handoff includes a written runbook, and you can host it anywhere, hire anyone to maintain it, or bring it back to us.
Is hosting included in the 15–20%?
No. The percentage pays for people's time. Hosting and monitoring are separate running costs. Hosting is typically $20–$200 a month for a small-business app, or roughly $5–$50 for a site built for under $5,000. Pythn can host the software for you or hand you the keys to run it yourself.
What happens if I skip maintenance?
Nothing, at first. The software keeps running while its foundations age out of support: Python 3.10 stops receiving fixes of any kind in October 2026. Skipped updates pile up until routine work turns into a project. For what else goes wrong, see why custom software projects fail.
Does Pythn offer maintenance after launch?
Yes. Every engagement includes 30 days of post-launch support. After that, it's a maintenance retainer or on-demand engagement — your choice. Either way you get direct access to the developers who built your software, with no tiered support desks and no ticket queues. The services overview covers what we build.