If you still run Dynamics NAV, you already know the pressure: older versions are out of mainstream support, customisations have piled up over the years, and nobody wants to be the person who breaks month-end. The good news is that a NAV to Business Central upgrade is a well-trodden path. The risk sits in planning, not in the technology.
Start with what you actually use
Most NAV systems carry a decade of customisations, and a surprising share are no longer used or have been replaced by standard features in Business Central. The first step is an inventory: every customisation, add-on and report, marked as keep, drop or replace with standard functionality.
This usually shrinks the work considerably, and it is the single biggest lever on cost.
Convert customisations into extensions
NAV customisations changed the base code. Business Central does not work that way: changes live in extensions written in AL, separate from the core. That is what makes Microsoft’s continuous updates possible without breaking your system.
Converting takes effort, but it is the point of the exercise. After it, upgrades stop being projects.
Plan the data, twice
Decide early how much history you need. Everything is possible, but full history costs time and money, and often is not needed once you keep the old system available for lookups. Whatever you choose, run the migration at least twice before go-live: once to find the problems and once to prove the fixes, reconciling record counts and balances each time.
Test with the people who use it
The best testers are the people who run your processes daily. Give them a test environment and their real tasks — a sales order, a purchase, a month-end close — rather than abstract test scripts. They will find issues no developer would spot.
Choose the go-live moment carefully
Cut over at a natural break in your financial calendar, never mid-period. Plan the quiet days around it, agree who decides to postpone if something is not ready, and keep the old system readable for a while afterwards.
What you gain
Beyond staying supported: cloud access, regular updates without upgrade projects, Power BI reporting on live data, Power Automate for approvals, and Copilot features that reduce manual data entry.
If you are weighing an upgrade, an assessment of your current system is the sensible first step. It tells you what to keep, what it will cost and how long it will take, before you commit to anything.