Quick answer. As of September 2026, Microsoft publishes a separate route into Dynamics 365 for each legacy product: Dynamics AX 2012 R2 and R3 upgrade into finance and operations apps, Dynamics GP and Dynamics SL 2015 or later migrate to Business Central online with built-in tools on SQL Server 2016 or later, Dynamics NAV must first be upgraded to Business Central on-premises, and Dynamics CRM or Dynamics 365 on-premises must be on version 9.0 or later to use Microsoft’s on-premises-to-online migration. Data from a system that is not a Microsoft product moves as a data migration into a new implementation, through the data management framework for finance and operations apps or configuration packages and templates for Business Central. Microsoft’s May 2026 US Government parity document lists Business Central as Not Available in GCC, GCC High and DoD, lists OnPrem to Online Migrations as Available in all three, and lists moving a finance and operations environment between geographies as Not Available or No Plans, so the target cloud is settled before the first system moves.
The board approved one line: move to Dynamics 365. The proposals that followed each quote one timeline for the whole estate. Your estate is not one system. An ERP runs at the parent, an older accounting system runs at the subsidiary you acquired, the sales and service teams run a CRM on servers you own, and one business still runs software from another maker. You suspect that is several migrations with different rules, and you are right to check before a date carries your name.
This guide takes each legacy system in turn: the route Microsoft publishes for it, the floor that route requires, and what changes if the data must stay in a US Government cloud.
Why a Move to Dynamics 365 Is Several Migrations, Not One
If the plan in front of you treats the estate as one migration, it has skipped the question Microsoft answers first: which product you are leaving. Microsoft’s migration overview states: “Depending on the on-premises solutions, organizations can either run the migration themselves or onboard to Microsoft’s migration services.” The route, the tools and the preconditions all change with the source system.
Whether to move a given system at all comes before the route. Microsoft’s implementation guide states: “Check whether your legacy system meets your business needs and whether your users like it. It’s the most important factor in deciding how to move to the cloud.”
This guide’s recommendation: list every legacy ERP and CRM system with its product name and version before anyone quotes a timeline. The version decides the path, and the path decides the plan.
If you are still deciding whether Dynamics 365 ERP is the right platform at all, Dynamics 365 ERP for the Regulated Enterprise: Modernizing or Replacing Legacy ERP covers that decision. This guide assumes it has been made.
The Path Table: From Each Legacy System to Dynamics 365
When the system list exists, each row below tells you which route it takes and the floor Microsoft states for that route. The table is this guide’s reading of Microsoft’s pages, not a Microsoft table, and each floor links to the Microsoft Learn page that states it.
| Legacy system | Microsoft’s path | The floor Microsoft states | Where the detail lives |
|---|---|---|---|
| Dynamics AX 2012 | Upgrade into finance and operations apps | Dynamics AX 2012 R2 or R3 only | Microsoft’s AX upgrade overview, linked in this row |
| Dynamics AX 2009 | A data migration through Microsoft’s data migration tool, not an upgrade | Data moves through the tool; no upgrade is listed | Microsoft’s migration overview, linked in this row |
| Dynamics GP | Built-in migration tools into Business Central online | GP 2015 or later, on SQL Server 2016 or later, compatibility level 130 or higher | Dynamics GP End of Life: What Microsoft Migrates to Business Central, and What It Leaves Behind |
| Dynamics NAV | Upgrade to Business Central on-premises, then switch to Business Central online | Customization handled by extensions; no data carried forward from code-customized tables | The next section of this guide |
| Dynamics SL | Built-in migration tools into Business Central online | SL 2015 or later, on SQL Server 2016 or later, compatibility level 130 or higher | The next section of this guide |
| Dynamics CRM or Dynamics 365 (on-premises) | Microsoft’s on-premises-to-online migration into Dynamics 365 online | Dynamics CRM V9.0 or Dynamics 365 (9.0/9.1) | Microsoft’s migration process overview, linked in this row |
| An ERP or CRM that is not a Microsoft product | A data migration into a new implementation | The data management framework for finance and operations apps; configuration packages and templates for Business Central | The FAQ at the end of this guide |
The AX row has two limits worth reading in Microsoft’s words. Microsoft’s migration overview states: “Currently, upgrades from Dynamics AX 2012 R3 and Dynamics AX 2012 R2 are supported.” For the older release, the same overview states: “You can also use the Microsoft Dynamics AX 2009 Data migration tool (DMT) to migrate your data from Dynamics AX 2009 to Dynamics 365.” Where the release is in doubt, Microsoft’s AX 2012 upgrade overview states: “If you aren’t sure whether your system can be upgraded, run the Upgrade analyzer tool.”
For GP, this guide carries Microsoft’s version and database floor and nothing more. Microsoft’s overview states: “You can use the built-in migration tools to migrate data to Business Central online from Dynamics GP 2015 and later versions.” On the database, Microsoft’s Migrate to Dynamics 365 online from Dynamics on-premises products page states: “The on-premises solution must use SQL Server 2016 or a later version, and the database must have compatibility level 130 or higher.”
CRM on-premises has one gate. Microsoft’s process overview states: “To perform the migration, your source environment must be a version of Dynamics CRM V9.0 or Dynamics 365 (9.0/9.1).” A CRM below that version reaches the program only after an upgrade on your own servers.
Software from another maker has no upgrade path, because there is nothing Microsoft can upgrade. Microsoft’s data management overview states: “By using the data management framework, you can quickly migrate reference, master, and document data from legacy or external systems.” That system becomes a new Dynamics 365 implementation with its data loaded, not a migration of the old application.
Dynamics NAV and Dynamics SL: The Two Paths No One Plans For
If a subsidiary runs Dynamics NAV, its route to the cloud has a stop on the way that estate plans tend to leave out. On Dynamics NAV, Microsoft’s migration overview states: “The final version was released in 2017, and extended support ends in January 2028.” Microsoft’s Business Central migration page states: “If you are currently on a version of Dynamics NAV, you must upgrade to Business Central on-premises, and then switch to Business Central online.”
The switch to online has a condition. Microsoft’s overview of on-premises migrations states: “You can upgrade to Business Central online from supported versions of Dynamics NAV if your application customization is handled by extensions.” The same overview states: “You can’t carry forward any data from tables with code customizations from Dynamics NAV.”
That last sentence turns a technical detail into a data decision. A NAV system customized in code, rather than through extensions, keeps the data in those tables behind when it moves online. This guide’s recommendation: inventory every NAV customization as an extension or as code before any date is set, and let the owners of the data in code-customized tables decide what happens to it.
Microsoft also lists an essential-data route, marked preview in its own list of next steps. Microsoft’s Business Central data migration page states: “Use the Business Central 14 Reimplementation tool to migrate only essential data (master data, opening balances, and setup) directly to the cloud without upgrading on-premises first.” Treat it as a preview option, not as the plan of record.
Dynamics SL follows the GP pattern. On SL, Microsoft’s migration overview states: “You can use the built-in migration tools to migrate data to Business Central online from Dynamics SL 2015 and later versions.” The same overview sets the same database floor for SL that it sets for GP: SQL Server 2016 or later, at compatibility level 130 or higher. An SL system below either floor is upgraded on-premises first, and that upgrade belongs in the plan before the migration does.
If the Data Must Stay in a US Government Cloud
If any of your contracts require the data to sit in GCC, GCC High or DoD, check the target applications before you choose a path, because the path table assumes the target exists. Microsoft’s US Government parity document, dated May 2026, states: “Microsoft strives to maintain functional parity across our localized data center deployments.” It defines its own status this way: “Not Available: This feature is currently unavailable in the Geo.”
Read one line per row, Microsoft’s May 2026 parity document lists these entries across its GCC, GCC High and DoD columns:
- Dynamics 365 Business Central: Not Available in GCC, GCC High and DoD.
- Dynamics 365 Finance and Dynamics 365 Supply Chain Management: Available in GCC and GCC High, and “Available – Pending IL5 Approval” in the DoD column.
- Dynamics 365 Sales Enterprise, Dynamics 365 Customer Service and Dynamics 365 Field Service: Available in all three.
- OnPrem to Online Migrations, a row under Common Platform Capabilities: Available in all three.
- F&O Environment Migration, a row under Geo to Geo Migrations: Not Available in GCC, and No Plans in GCC High and DoD.
Read together, as this guide reads them and not as a sentence Microsoft wrote: as of the May 2026 document, a GP, NAV or SL subsidiary cannot follow its Business Central path into a US Government cloud, and a finance and operations environment stood up in the wrong cloud has no listed move to another geography. The OnPrem to Online Migrations row names no product, so this guide does not extend it to the AX upgrade or to the Business Central tools. The document gives no date for any change, and this guide predicts none.
Which cloud your data must sit in is not a question this guide answers. That determination belongs to your contracting officer, the contract clause and your compliance lead. Microsoft also sets its own eligibility rule for the US Government clouds, and Hire a Dynamics 365 Implementation Firm for a Government Contractor Environment quotes that rule in full.
What Has to Be True Before Any Path Opens
When a system clears its version floor, it has cleared the first gate, not the last. Microsoft’s implementation guide names what to know before leaving on-premises, and its words are more useful than a paraphrase.
On data, Microsoft’s implementation guide states: “Know your data category, flow, transformations, location, and encryption before and after the migration.” On customization, the same guide states: “Look for deprecated, unsupported, or risky customizations and patterns that could affect security or performance.”
For how the system will behave afterward, Microsoft’s cloud move guidance states: “You might need to deal with some changes in process, performance, and usability due to latency, service protection limits, or license capacity.” On where the data lands, the same guide states: “Choose a cloud platform that can store and process your data safely and legally.”
Beside those sit each path’s own floor from the table: the AX release, the GP and SL database version, the NAV extension rule and the CRM version. A system that misses a floor needs an upgrade on your own servers first, and that upgrade is its own piece of work with its own plan.
Existing interfaces are a separate workstream on every path, because each legacy system feeds and is fed by others. i3solutions has delivered Dynamics 365 integration engagements for regulated enterprises across healthcare, defense and aerospace manufacturing, and financial services. How to map those interfaces and decide what happens to each one is covered in Who Handles Microsoft Integration When an ERP or CRM Migration Creates Pressure?
What Drives Cost and Timeline, Without a Number
If a proposal gives one figure for the whole estate, ask which of these drivers it priced, because each one traces to a condition in Microsoft’s migration overview or to your own inventory:
- How many legacy systems the estate holds, and which path each one takes in the table above.
- Whether each system meets its floor today or needs an upgrade on your own servers first: the AX release, the GP and SL database version, the CRM version, and the NAV route through Business Central on-premises.
- How much NAV customization is code rather than extensions, which decides what data can move online.
- How much history must move rather than be archived, with Microsoft’s preview essential-data route as the contrast.
- The integration inventory from the previous section.
- The target cloud, settled against the parity document before any path is chosen.
A defensible number comes from the per-system inventory, not from a single estimate for the estate. This guide gives no price, range or duration, because none of the drivers above is known until the inventory exists.
What a First Conversation With i3solutions Produces
If you bring a system list to a first conversation, you should leave with a path per system, not a pitch. i3solutions migrates on-premises Dynamics CRM to Dynamics 365 in the cloud and upgrades on-premises Dynamics instances, as project work, with embedded specialists available where your team needs them. All i3solutions Dynamics 365 developers and consultants are U.S.-based. i3solutions delivers through its Expert Delivery Model, a four-phase methodology (discovery, architecture, build, and knowledge transfer) with explicit exit criteria and delivery assurance at every handoff.
The first working session produces four things for your estate: an inventory of every legacy system against the floor Microsoft states for its path, a path per system, a check of the target applications against Microsoft’s US Government parity document where your contracts require a government cloud, and a sequence that puts on-premises upgrades before the migrations that depend on them. The decisions stay with your team, and so does the estate once each system is live.
i3solutions’ wider Dynamics 365 practice is described at Enterprise Dynamics 365 Development Services That Align CRM and ERP to How You Operate. To put your own system list against Microsoft’s paths, start with the contact form.
When This Guide Is the Wrong Starting Point
If your estate is a single system with its own guide, start there: a GP-only estate has the GP guide linked in the path table. If the platform decision is still open, the ERP platform guide linked earlier comes first. If a subsidiary sized for Business Central must keep its data in a US Government cloud, the path table does not solve that; your compliance determination and the parity document come first.
Migrating is also the wrong call for some systems. Microsoft’s implementation guide makes fit to business needs the most important factor in deciding how to move, and read the other way, that factor can say not yet. A legacy system that still meets its business needs and has support left may stay while the others move: for Dynamics NAV, Microsoft’s migration overview gives January 2028 for the end of extended support, and for GP the dates are on the GP guide.
Key Takeaways
If you have one meeting to settle the plan, carry these points from Microsoft’s migration overview and May 2026 US Government parity document:
- A move to Dynamics 365 is one migration per legacy system, each on the route Microsoft publishes for that product.
- Dynamics AX 2012 R2 or R3 upgrades; Dynamics AX 2009 moves its data through a tool; GP and SL 2015 or later use built-in tools on SQL Server 2016 or later at compatibility level 130 or higher.
- Dynamics NAV goes through Business Central on-premises first, and data in code-customized tables does not move online.
- Dynamics CRM on-premises must be on version 9.0 or later for Microsoft’s on-premises-to-online migration.
- As of May 2026, the parity document lists Business Central as Not Available in GCC, GCC High and DoD, so settle the target cloud first.
Frequently Asked Questions
Can we move Dynamics NAV straight to Business Central online?
No. According to Microsoft Learn, a Dynamics NAV system must first be upgraded to Business Central on-premises and then switched to Business Central online. Microsoft Learn adds that the upgrade to online applies where customization is handled by extensions, and that data from tables with code customizations in Dynamics NAV cannot be carried forward.
What does Dynamics GP or Dynamics SL need before it can move to Business Central online?
A supported version and a supported database. According to Microsoft Learn, the built-in migration tools move data to Business Central online from Dynamics GP 2015 and later and from Dynamics SL 2015 and later, and the on-premises solution requires SQL Server 2016 or a later version with a database at compatibility level 130 or higher.
Is Business Central available in GCC or GCC High?
Not as of Microsoft’s May 2026 document. According to Microsoft’s US Government parity document dated May 2026, Dynamics 365 Business Central is listed as Not Available in GCC, GCC High and DoD, and the document defines Not Available as a feature currently unavailable in the Geo. The document gives no availability date, and this guide does not predict one.
How does data from a system that is not a Microsoft product get into Dynamics 365?
As a data migration into a new implementation. According to Microsoft Learn, the data management framework migrates reference, master and document data from legacy or external systems into finance and operations apps, and configuration packages and templates migrate data from a non-SQL source into Business Central on-premises.
