Microsoft Dynamics NAV to Business Central Cloud Migration

What happens to C/AL customizations?

In NAV, customizations were generally made by modifying base objects: tables, pages, codeunits and reports. That model is not compatible with Business Central Cloud, where the base code is locked and every extension must be independent and upgrade-safe.

During the audit, each C/AL modification is classified into one of these categories:

• Already covered by standard Business Central functionality
• Reproducible with a table extension, page extension or report extension
• Requires rewriting on events (posting, validations, workflows)
• Obsolete or replaced by a native ERP feature

This analysis avoids rewriting unnecessary code and is the basis of the effort estimate. It is covered in more depth on the AL extension development page.

"Line Discount %" :=
   GetCustomerDiscount("Sell-to Customer No.");

codeunit 50100 "VPC Sales Discount"
{
    [EventSubscriber(ObjectType::Table,
        Database::"Sales Line",
        'OnAfterValidateEvent', 'Quantity',
        false, false)]
    local procedure ApplyDiscountOnQuantity(
        var Rec: Record "Sales Line")
    begin
        Rec."Line Discount %" :=
            GetCustomerDiscount(Rec."Sell-to Customer No.");
    end;

    local procedure GetCustomerDiscount(
        CustomerNo: Code[20]): Decimal
    var
        Customer: Record Customer;
    begin
        if Customer.Get(CustomerNo) then
            exit(Customer."VPC Discount %");
        exit(0);
    end;
}

Instead of modifying the base table, the logic hooks into an event and new fields are added from an extension.

How it is done

For NAV 2018 and later, the cloud migration tooling replicates the on-premises database and allows copying entire companies. For reimplementations, configuration packages load masters and opening balances are posted through opening entries. Large volumes can be migrated with codeunits and APIs.

Validation

• Row counts and checksums per table and per company
• Reconciliation of G/L and inventory balances
• Review of customer and vendor balances and open documents
• Formal business sign-off before cutover

Cutover plan

• Operational freeze and period close
• Final data synchronization (delta)
• Validation and sign-off
• Opening of Business Central Cloud and go-live support
• Documented rollback plan

Downtime

With the migration tooling and incremental replication, the final cutover is reduced to a bounded window: typically one night or a weekend. The larger the data volume and the more integrations to reconnect, the longer the window needed.

Phased migration allows parallel validation so the cutover is reached with the lowest possible risk. Downtime does not depend on technology alone: business validation time also matters.

Licensing

Business Central Cloud is purchased as a subscription, not a perpetual license. Microsoft publishes transition programs for NAV customers. License cost depends on the number of users and the edition purchased.

Migration services

The service includes assessment, customization conversion, data migration, reports, integrations, testing and cutover. It is quoted by scope and by phase, so you know what is delivered at each stage.

See the migration cost guide →