Upgrade steps for Business Central, from assessment to go-live

Business Central upgrade steps: assess your system

Begin by noting the exact version and build, the database size, the number of companies and the add-ons. Then compare your objects with the standard ones for that version. In NAV systems, people changed C/AL code directly, so this shows how much custom work exists.

Next, sort each customization into one of four groups. Standard Business Central may now cover it. An AppSource app may replace it. You may still need it and must rebuild it. Or nobody uses it any more. Talk to users as well, because many old changes serve a process that stopped long ago.

Choose an upgrade path to Business Central

Microsoft documents which versions can upgrade straight to the latest release. Older NAV versions usually pass through one or more stops on the way. The Microsoft Learn upgrade pages list the supported paths. The path decides how many conversion rounds your data goes through.

Another route is reimplementation. You set up a fresh company and bring over master data and balances, instead of upgrading the database. It suits heavy customization, poor data or a chart of accounts that needs a redesign. Compare both routes during the assessment and write down why you chose one.

Rebuild customizations as AL extensions

Current Business Central does not let you change the base application the way NAV did. Instead, developers rebuild custom fields, pages, logic and reports as AL extensions. They hook into events in Microsoft's code. Table and page extensions add fields. Upgrade code then moves your existing custom data into the new tables.

This is normally the largest part of the project. Microsoft supplies a tool that turns C/AL objects into AL syntax as a starting point. Developers then reshape the result into clean extensions. Rebuild reports with Word, Excel or RDLC layouts. Add-on vendors supply their own upgraded versions.

Business Central upgrade steps: upgrade the data and test

Once the extensions are ready, take a copy of the production database through the technical upgrade. Then run the data upgrade, which runs Microsoft's code and yours for every company. Do this on a test server first. Fix any errors in the extensions or the data, and repeat the run until it is clean.

Users then test the upgraded copy. They post documents, run month-end routines, print every form and compare reports with the old system. Permissions need care, because permission sets have changed a lot since NAV. Finally, timing the full run tells you how long the live system will be down at cutover.

Moving online after the on-premises upgrade

Once your database sits on a supported on-premises version with extensions only, the cloud migration tool can copy the data online. Many companies combine the upgrade and the move in one project. In that case, the on-premises result is only a stepping stone.

After that, upgrades become updates. Microsoft applies two release waves a year plus monthly updates. You choose the update window in the admin center. Then you test your extensions in a sandbox or preview environment beforehand. Keep the test scripts from the upgrade, because they become your checklist for each wave.

Questions about the Business Central upgrade steps

Can we upgrade straight from an old NAV version to Business Central online?

Not in one jump. First, you upgrade the database on-premises to a version the cloud migration tool supports, with customizations turned into extensions. Then you migrate the data online. For very old versions, a fresh start is sometimes the more sensible route. Weigh both routes during the assessment, before any conversion work starts.

What happens to our C/AL modifications?

Assess each one. Some go away because standard features now cover them. Others are replaced by add-ons. The rest are rewritten as AL extensions. None carries over unchanged, because current Business Central does not run C/AL code. So expect the rebuild of custom logic to be the biggest part of the plan, and plan your testing around it.

Will users notice a big difference after the upgrade?

Yes, if they come from the NAV Windows client. Business Central uses a browser client with a different layout, search, personalization and Excel integration. But the business logic feels familiar. A short training session for each role before go-live helps a lot. As a result, the first week after cutover runs far more smoothly for everyone.

Is an upgrade or a fresh implementation better?

An upgrade keeps all your history and suits systems with moderate customization and sound data. A fresh implementation suits systems where setup, accounts or processes need a rethink. Base the choice on the assessment, and list the trade-offs of each route before any work begins. Then decide with the facts in hand.

Do add-ons upgrade automatically?

No. Each add-on vendor supplies a version for current Business Central, often as an AppSource app, and its data needs an upgrade too. Some older add-ons no longer exist. So check every add-on early, because a missing one can change the whole plan. List them all in the first step, the assessment.

Related upgrade topics for Business Central

These related pages cover NAV and Business Central upgrades, how Navision relates to today's product and what version numbers mean for planning. Read them next, so your upgrade plan fits your own timing, your add-ons and your team. For the product detail, see Upgrading to Business Central on Microsoft Learn.