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The real difference is operational, not functional
Open Business Central online and on-premises next to each other and a finance user will struggle to tell them apart. The same pages, the same posting routines, the same reports. What differs is everything behind the screen: who patches the operating system, who sizes SQL Server, who tests and applies each update, and who restores the database at two in the morning when something goes wrong.
Online, Microsoft does that work on Azure. You manage environments through the Business Central admin center, choose an update window, and keep sandboxes for testing. On-premises, your IT team or a hosting partner owns the servers, the licences for Windows Server and SQL Server, the backup routine and the upgrade schedule.
That makes the decision less about features and more about whether operating an ERP platform is something your company wants to be good at.
Online and on-premises side by side
What online takes off your plate
No upgrade projects
On older on-premises systems, a version upgrade was a project in its own right. Online, updates arrive on a schedule and your job shrinks to testing extensions in a sandbox before the window.
Security patching
Operating system, database and application patching is Microsoft's job. Your job is user access, permission sets and multi-factor sign-in through Microsoft Entra ID.
Hardware refresh cycles
No servers to replace, no SQL Server licences to renew, and no capacity planning for month-end peaks.
Faster test environments
A sandbox copy of production can be made from the admin center for training, testing an app or trying a new process, then deleted when you are done.
When on-premises still earns its place
- ✓Sites with unreliable internet, such as remote plants or yards, where the ERP must keep running during an outage.
- ✓Contracts or regulations that require data to stay on hardware you control, and where Microsoft's cloud compliance commitments do not satisfy the customer or regulator.
- ✓Heavy reliance on direct SQL reporting or .NET components that would take significant effort to rebuild as APIs and cloud-safe extensions.
- ✓A large recent investment in on-premises infrastructure and an IT team that already runs it well, where moving now would waste that spend.
- ✓A modified base application carried over from NAV that cannot be rewritten as extensions yet. This should be a temporary state, not a strategy.
Moving an on-premises system to online
- 1
Inventory the customizations
Every extension and modification is listed and checked against cloud rules. Anything using .NET or direct database calls is redesigned.
- 2
Check version and data
Microsoft's cloud migration tool replicates data from supported on-premises versions into an online environment. Older versions are upgraded first.
- 3
Replicate and test
Data is copied to an online sandbox, reports and integrations are tested, and users try their daily tasks there.
- 4
Switch over
A final replication runs, the on-premises system is set to read-only, and users sign in to the online environment.
Cloud and on-premises questions from IT and finance
Is our data safer on our own servers?
Not automatically. Microsoft runs Business Central online on Azure with dedicated security teams, encryption and physical controls few mid-sized companies can match. What stays your responsibility in both cases is who has access and with which permissions. On-premises can be very secure, but only when patching, backups and monitoring are done consistently.
Can we still customize Business Central online?
Yes, through AL extensions, the same way on-premises extensions are built. The cloud does not allow editing the base application, .NET interop or direct database access, so a few older techniques are off the table. In practice those limits are what keep online updates painless.
Can we report straight from the database online?
Not with direct SQL. Online data is reached through API pages, OData web services, Power BI apps and the Excel add-in. For heavy analytics, data can be exported to Azure storage or a data lake. Teams used to writing SQL queries against the ERP need a short adjustment.
What about a partner-hosted private cloud?
That is on-premises software running in someone else's data centre. It removes the hardware from your office but keeps the upgrade and patching work, and you still do not get the features reserved for the online service. It can be a sensible stepping stone, but it is not the same as Business Central online.
Can we move from online back to on-premises?
It is possible to get your data out, and Microsoft provides ways to export a copy of an online database, but it is uncommon and involves real effort. Most companies that go online stay there. If an on-premises requirement might appear later, raise it before the decision, not after.
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