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title: Business Central 2021 release wave 1
summary: Upgrading on-premises Business Central to 2021 release wave 1 (version 18) from versions 14, 15, 16 and 17. It answers questions on upgrade paths, C/AL to AL conversion, permission set migration, moving tables between extensions, and the upgrade compatibility matrix.
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    - https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-technical-upgrade-v18
    - https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-overview-v18
    - https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-to-microsoft-base-app-v18
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    - https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-unmodified-application-to-v18
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---

# Business Central 2021 release wave 1

> Upgrading on-premises Business Central to 2021 release wave 1 (version 18) from versions 14, 15, 16 and 17. It answers questions on upgrade paths, C/AL to AL conversion, permission set migration, moving tables between extensions, and the upgrade compatibility matrix.

Path: [Business Central on-premises](../../../business-central-on-premises.md) > [Upgrade](../../upgrade.md) > [Earlier versions](../earlier-versions.md) > Business Central 2021 release wave 1 · tier official · system platform · narrative reviewed (checked by Opus)

## Overview

This section documents the upgrade to Business Central 2021 release wave 1 (version 18) for on-premises deployments. Start with "Upgrade to Business Central 2021 Wave 1", which describes the paths: a technical upgrade, or application refactoring to the system application. "Install a version 18 update" covers applying a version 18 update to an existing installation.
The source version decides which page to follow. From versions 15, 16 or 17 there is a technical upgrade page and a full base application upgrade page. From version 14 there are three routes: an unmodified C/AL application, a customized C/AL application moved to the Microsoft Base Application, and a technical upgrade with C/AL converted to AL.
Supporting pages cover code conversion with Txt2Al, upgrading permission sets to AL objects, and moving tables and fields between extensions with migration.json (down or up the dependency graph). The compatibility matrix helps plan which versions can be upgraded to which.

## Key points

- Version 18 upgrade paths: technical upgrade, or application refactoring to the system application.
- Versions 15, 16 and 17 have a technical upgrade page and a full base application upgrade page covering extension publishing, tenant synchronization, data upgrade, control add-ins and license import.
- Version 14 has separate procedures for unmodified C/AL apps, customized C/AL apps moved to the Microsoft Base Application, and a technical upgrade to version 18.
- Code Conversion from C/AL to AL uses the Txt2Al tool, and covers .NET interoperability and test library conversion.
- Permissions move from legacy data-based permissions to AL objects (Permission Set and Permission Set Extension).
- Moving tables and fields between extensions uses migration.json. Moving up the dependency graph needs a two-stage process with a transition extension.
- Customized version 14 upgrades use DestinationAppsForMigration and table migration extensions.
- The compatibility matrix lists minimum update versions for upgrades. Upgrades from version 24 or earlier must target version 25 first.

## Learn pages

- [Business Central Upgrade Compatibility Matrix](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-v14-v15-compatibility): Provides an overview of the Business Central versions and their compatibility
- [Code Conversion from C/AL to AL](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/devenv-code-conversion): Description of the conversion process from C/AL to AL.
- [Install a version 18 update](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrading-cumulative-update-v18): This article describes the tasks required for getting the monthly version 18 update applied to your Dynamics 365 Business Central on-premises.
- [Migrating Tables and Fields Between Extensions](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/developer/devenv-migrate-table-fields): Explains how to migrate tables and fields from one extension to another.
- [Moving Tables and Fields to Extensions Down the Dependency Graph](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/developer/devenv-migrate-table-fields-down): Explains how to move tables and fields from an extension to another extension that is down the dependency graph.
- [Moving Tables and Fields to Extensions Up the Dependency Graph](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/developer/devenv-migrate-table-fields-up): Explains how to move tables and fields from an extension to another extension that is up the dependency graph
- [Technical Upgrade From Version 14 to Version 18](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-technical-upgrade-v14-v18): Describes how to do a technical upgrade from Business Central 14 to 18
- [Technical Upgrade from Version 17 to Version 18](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-technical-upgrade-v18): Describes how to do a technical upgrade from Business Central V15, 16, and 17, to V18
- [Upgrade to Business Central 2021 Wave 1](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-overview-v18): Provides an overview of Business Central 2021 release wave 1 upgrade
- [Upgrading customized C/AL application to Microsoft Base Application for version 18](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-to-microsoft-base-app-v18): Describes how to do an upgrade from a customized Business Central 14 to Microsoft Base Application for version 18
- [Upgrading Permission Sets and Permissions](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-permissions): Describes how to upgrade permissions and permission sets
- [Upgrading Unmodified C/AL Application to Version 18](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-unmodified-application-v14-v18): Describes how to upgrade an unmodified Business Central 14 application to version 18
- [Upgrading Version 15, 16, or 17 Base Application to Version 18](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/upgrade/upgrade-unmodified-application-to-v18): Describes how to upgrade an unmodified Business Central 15, 16, or 17 application to version 18

Source: Microsoft Learn (CC BY 4.0). Descriptions are Learn's own.