Your mobile app goes live and everyone treats the budget as closed. That is a mistake. A 20,000 EUR app generates 3,000 to 4,000 EUR per year in maintenance, and that figure almost never appears in the original proposal. This guide breaks down what the 15-20% annual rule actually covers, what happens if you ignore it, and which contract model suits an SME.
How much does it cost to maintain a mobile app per year?
The rule we use when quoting is simple: set aside 15% to 20% of the development cost every year for maintenance. An 8,000 EUR app means 1,200 to 1,600 EUR per year. A 20,000 EUR app, 3,000 to 4,000 EUR. A 50,000 EUR app, 7,500 to 10,000 EUR. This is not a number invented to sell contracts: it is what it costs, year after year, to keep an app working on operating systems that change every twelve months and in stores that keep tightening their requirements.
The exact percentage depends on whether the app has its own backend, how many external integrations it uses (payments, ERP, maps, push notifications) and how often you ship releases. A catalogue app with no server can stay close to 10% per year. An ordering app connected to your ERP with a payment gateway gets closer to 25%. If you are still at the budgeting stage, first read how much it costs to develop a mobile app, because the architecture decisions you make there set your maintenance bill for the next five years.
Where does the money go? Line-by-line breakdown
The biggest line item is mandatory operating system updates. Apple ships a major iOS version every September and Google requires apps to target a recent Android version to remain visible on the Play Store. Every year the app has to be recompiled, tested on new devices and patched where things break: permissions, notifications, retired APIs. In a typical SME app this consumes 30% to 40% of the annual maintenance effort.
The second line item is third-party libraries and services. A modern mobile app drags along 30 to 80 dependencies: payment SDKs, maps, analytics, push notifications. Each one publishes security patches and retires old versions without asking your opinion. Add the signing and notification certificates that expire every year and, if nobody renews them, take entire features down overnight.
The stores also cost money and attention. Apple charges 99 dollars per year for a developer account and Google 25 dollars as a one-off payment. The fees are not the expensive part; the policy changes are: privacy forms, data safety declarations, reviews that can reject an urgent update. Someone has to stay on top of all this, and that someone bills hours.
Then there is the line item everyone remembers too late: bugs and servers. Errors show up with real usage, not in testing, and fixing them quickly is what prevents one-star reviews. If the app has a backend, add hosting (30 to 150 EUR per month for a typical SME), backups, monitoring and SSL certificate renewals. Backends fail silently, and when they do, the app stops working for everyone at once.
What happens if you stop maintaining your mobile app?
The first thing that happens is you disappear from the stores. Google hides apps that do not target a recent Android version from new Play Store users, and Apple removes apps that have gone years without updates and barely register downloads. You do not need to do anything wrong: doing nothing is enough. The ordering app of a distribution company sat untouched for two years and quietly stopped accepting sign-ups from sales reps with new phones; nobody knew why until the project was audited.
The second thing is that catching up costs more than keeping up. Bringing an app abandoned for two years up to date in one go (two iOS versions, two Android versions, dozens of outdated libraries) typically costs 30% to 40% of the original development budget. That is more than those two years of retainer would have cost. Maintenance is not an expense you can avoid, it is an expense you can postpone with interest.
Monthly retainer or hour bank? The contract models
The monthly retainer is the model we recommend for apps that support operations: from 500 EUR per month you get proactive monitoring, operating system and library updates, priority bug fixing and a predictable cost you can budget in January. The point is that someone watches the app before it fails, not after. For a 20,000 EUR app, a retainer of 500 to 700 EUR per month lands exactly within the 15-20% annual rule.
An hour bank works for low-risk internal apps: you buy a package of hours and burn them as needed. The problem is structural: nobody reviews anything proactively, so the hours get spent putting out fires instead of preventing them. The third model, paying per incident (one-off fixes from 300 EUR), is the most expensive over time, because you always step in late, with the app already down.
Whatever the model, the contract matters as much as the price: a clear scope of what is and is not included, agreed response times, a monthly report of work done and full access to the repository, because the code is yours. How to fit all this into your budget and which clauses to avoid is covered in detail in our guide on software maintenance costs, budgets and contracts.
How do you reduce the maintenance bill from day one?
Cheap maintenance is decided during development. A cross-platform build with Flutter or React Native maintains one codebase instead of two, which cuts the annual bill by 30% to 40% compared with two separate native apps. Fewer dependencies, a simple architecture and automated tests also reduce the cost of every September update.
And choose carefully who maintains it. When the team that built the app is the same one maintaining it, every intervention is faster because nobody has to rediscover the code. At ASD Solutions the senior engineer who quotes the project is the one who delivers and maintains it, with no subcontracting, and the code always lives in your repository. If you want to switch providers tomorrow, you take everything with you, no penalties and no technical hostages.
Frequently asked questions
How much does mobile app maintenance cost per month?
Between 15% and 20% of the development cost per year, spread across months. For a 20,000 EUR app that is roughly 250 to 330 EUR per month in real cost, although professional retainers start at 500 EUR per month because they include proactive monitoring, updates and priority support, not just loose hours.
Do I have to update my app every year?
In practice, yes. Google requires apps to target a recent Android version to stay visible on the Play Store, and Apple ships a major iOS version every September. Skipping one year is usually recoverable; skipping two turns the update into a mini-project costing thousands of euros.
What happens if I leave my app unmaintained for two years?
The Play Store will hide it from new users, recent phones will start failing and your libraries will pile up unpatched vulnerabilities. Bringing it up to date will cost 30% to 40% of the original development budget, more than maintaining it for those two years with a retainer from 500 EUR per month.
Which suits me better, a retainer or an hour bank?
It depends on how critical the app is. If it supports orders, routes or invoicing, choose a retainer from 500 EUR per month with monitoring included. If it is an internal app with sporadic use, an hour bank may be enough. What we do not recommend is waiting for the breakdown: one-off fixes start at 300 EUR and always arrive late.
Does maintenance include new features?
No. Maintenance covers corrective work (bugs), adaptive work (new iOS and Android versions) and preventive work (dependencies and security). New features are quoted separately as evolutions: in our case, at a fixed price from 1,500 EUR for a medium build taking 3 to 6 weeks.
