Clean Start vs Upgrade: 2 Paths from Dynamics NAV to Dynamics 365 Business Central

If you are on Dynamics NAV and preparing to move to Dynamics 365 Business Central, it can be tough to know which of the two approaches you should take for this change.

  • Clean Start: Also called a reimplementation, a clean start lets you optimize and update your business processes with fresh data and updated configurations, and lets you keep your historical data through, for instance, Azure Data Lake.
  • Upgrade: Transfers your existing processes from NAV into Business Central, and brings your historical data inside Business Central.

As the Practice Lead for Dynamics 365 Business Central, I have overseen dozens of projects moving NAV customers to Business Central. There have been significant changes in best practices and technology in recent years, and those changes affect which choice is now right for many companies.

Table of Contents

Clean Start (Reimplementation)
Pro – historical data directly inside Business Central
Pro – historical data can be available without “cluttering” your new system.
Pro – procedures and processes stay as is
Pro – opportunity to optimize and better fit your ERP to your new needs
Pro – a shorter timeline if your system is simpler than most
Pro – immediately take advantage of new functions and technology
Pro – fresh start with data volume
Con – missed opportunity to optimize your processes
Con – more up-front effort needed for your team to re-evaluate your processes


Read on for deeper explanations of the options, what’s changed over time, and how to decide which is best for you.

What Is a NAV to Business Central “Clean Start” Reimplementation?

In a clean start, we migrate master data records like your customers, vendors, items, chart of accounts, etc., along with GL net change balances and sub-ledger open balances like AR, AP, fixed assets, and item quantities.

We also work with you to determine the best way to optimize your processes and leverage Business Central’s new functionality. This means Business Central can better elevate your day-to-day and support your strategy.

The New, Built on the Old

A clean start is sometimes called a reimplementation because, at a technical level, it works like a new implementation. However, the concepts behind Business Central are essentially built on everything you already know about NAV.

You already know how components like dimensions work or how value entries are attached to item ledger entries, so your company will not have to learn the concepts of a totally new system. Much will be familiar.

Keeping Historical Data in a Clean Start

Technically, a clean start does not bring any historical data directly into Business Central. However, since early 2023, improvements in best practices and technology mean that a clean start can still make your historical data easily available to your team by leveraging Azure Data Lake or a trusted ISV option.

In my experience, for most companies, having the data available in this way is as good as or even better than having the old data from NAV directly in Business Central.

Optimize and Reimagine Your Processes

The clean start path to Business Central provides the opportunity for you to reimagine and optimize what you already know and love about NAV into a fresh environment.

For instance, your business may have changed in the years since your NAV implementation. Perhaps some of your current dimensions or financial reports are no longer relevant. In that case, the clean start gives us a chance to realign your ERP with your new needs and strategy.

Steps for a Clean Start

A clean start typically involves the following steps:

  • Analysis.
    • This is the opportunity to fit new business processes into Business Central.
    • This also helps identify any gaps or customizations and determines what the options are for meeting those needs.
  • Solution modeling.
    • Design and configuration – data migration via templates.
    • Customizations.
  • Deployment.
    • User training.
    • User acceptance testing.
  • Go live.
    • Balance forwards for customers, vendors, item quantities, etc., and monthly net changes for the general ledger.


An upgrade is a technical process that essentially takes your data from NAV and runs it through development tools that massage that data and then fit it into Business Central. It’s very much a technical process that is essentially lifting and shifting your data into Business Central.

As compared to a clean start, an upgrade does not provide the opportunity to optimize your processes and adapt to changes in your business needs since your original NAV implementation.

Upgrade Steps

An upgrade typically involves the following steps:

  • Create a test server and restore a backup of NAV onto it.
  • Install the set of migration tools from Microsoft.
  • Perform the Code/Object upgrade.
    • We track the length of time for each technical step. This is needed for planning the upgrade on the production database.
  • Reproduce any needed customizations as extensions.
  • Implement any add-ons.
  • Validation and testing.
  • User training.
  • User acceptance testing.
  • Perform a second Code/Object upgrade.
    • This is to confirm timings and to handle any Business Central updates that may have happened in the meantime.
  • Planning upgrade for the live database.
  • Perform upgrade on live database.
  • Go live.

Customizations, Extensions, and 3rd-Party Products

Neither a clean start nor an upgrade will automatically bring your customizations and any 3rd-party solutions (often called ISVs or add-ons) into Business Central.

There are very good reasons for that: Business Central has significant new functionality compared to NAV, and there are also many new 3rd-party add-ons.

As part of your process of moving from NAV to BC, we’ll evaluate your current customizations and 3rd-party products to determine which of your needs may already be covered by Business Central itself. For the remaining needs, we can then evaluate the best options for you. Three examples may help illustrate this:

Approvals: Did you have to program and customize for purchase order approvals or general journal approvals in NAV? That’s now a standard function within Business Central.

AP automation: Do you currently rely on a customization for scanning and importing vendor invoices? There are now several apps available for Business Central which cover that functionality well.

Custom reports: We find that about half of the custom reports customers have in NAV are no longer needed, or that customers moving to Business Central take the opportunity to introduce a new reporting tool. A reporting tool can let you maintain, develop, and analyze data utilizing your own internal resources and experts to address your reporting needs, rather than have us redevelop these reports.

How Long Does It Take?

We find that both clean starts and upgrades take around 6 months. That general timeline is very much dependent on the quality of the data, the number of customizations, the number of add-ons, and customer availability.

Although for a simpler NAV environment an upgrade may have less work involved than a clean start, over time we have found that most companies who are interested in the upgrade path have more complex environments (more customizations, etc.). In fact, those companies’ systems are usually so complex that a clean start would be equally fast for them.

So on balance, for most companies, I no longer consider length of time a pro or con for deciding between clean start and upgrade.

Which Path Is Right for You?

In general, as of 2024, I would now recommend the clean start option in more cases than the upgrade option.

Most businesses have changed enough since they deployed NAV that they will benefit from a clean start, re-envisioning the processes in their ERP. And the timeline and availability of historical data are roughly equal between the two options.

However, your company’s decision should be based on factors specific to you, such as:

  • The current version of NAV you are using.
  • The level of customization and integration in your NAV system.
  • Business requirements and processes that have changed or evolved since your original implementation.
  • The quality and relevance of your historical data and master records – is there a reason your staff need the historical data in Business Central rather than accessible in a related system?
  • The opportunity to optimize and take advantage of the new functionality and technologies in Business Central.

How Can We Help?

At Encore, we have the experience and expertise to help you evaluate how your needs and technical situation match up to the pros and cons of the two options. We can help you:

  • Consider the pain points in your current system, especially the relevance of your current dimensions and the effectiveness of your financial reports.
  • Analyze your NAV system and identify the gaps and opportunities for improvement.
  • Design, configure, and extend Business Central to meet your business needs and goals.
  • Train and support your users on the new environment and functionality.
  • Optimize and enhance your Business Central system with add-ons and integrations.

If you have any questions or need assistance with your path to Dynamics 365 Business Central, please contact us anytime. We would love to hear from you and help you make the best decision for your business.

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