Why No. Series Break After Upgrading to Business Central 27 (And How to Fix It)

Hi All,

During this weekend we did multiple customers upgrade to Business Central 27 Cloud customers.

They did basic testing and expected upgrade to go smoother, but an unexpected issue was found after upgrade to Business Central 27.

Impact:

• Business Central On-Prem
• Business Central SaaS

In this article we will discuss, how to solve it before Microsoft fix the code for the upgraded environments.

Business Central 27 enforces No. Series validation during insert, causing errors where BC 26 allowed missing setup.

Introduction

Upgrades are supposed to improve stability—not break working systems.

Yet many teams upgrading from Business Central 26 to 27 suddenly face No. Series errors on master 

records that previously worked fine.

This is not accidental. It’s a behavioral change with real upgrade consequences.

Why Do No. Series Fail After Upgrade?

What Changed in BC 27?

Business Central 27 validates No. Series earlier and more strictly.
Implicit numbering paths that existed in BC 26 no longer pass validation.

Why BC 26 Did Not Fail

• Deferred validation

• Implicit assignment

• Lenient insert logic

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Which Records Are Affected?

• Master entities without explicit No. Series

• Custom tables relying on default behavior

• Legacy extensions written against older assumptions

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Step-by-Step Fix

1. Audit all master entities

2. Validate setup tables

3. Refactor insert logic

4. Enforce No. Series assignment before insert

5. Retest upgrade scenarios

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Code Changed Done by Microsoft

BC 26 Code

if NoSeriesCode <> '' then

                TestManualInternal(NoSeriesCode, StrSubstNo(CannotAssignManuallyErr, NoSeries.FieldCaption("Manual Nos."), NoSeries.TableCaption(), NoSeries.Code));

BC 27 Code

TestManualInternal(NoSeriesCode, StrSubstNo(CannotAssignManuallyErr, NoSeries.FieldCaption("Manual Nos."), NoSeries.TableCaption(), NoSeries.Code));

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How to Fix with Setup 

• Navigate to Setup.
• Create a new series and assign to setup.
• Make sure New Series have only Manual No Enabled (other details keep standard)

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Common Mistakes

• Blaming users instead of setup

• Patching with hardcoded values

• Ignoring extension insert triggers

• Skipping regression testing

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When NOT to Apply This Fix

• Manual numbering designs

• External numbering integrations

• Tables intentionally without No. Series

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FAQ

Is this expected behavior?
Yes, but the upgrade impact was poorly communicated.

Should Microsoft have handled this better?
Yes—backward compatibility should have been managed.

What is the error message? The No. Series does not exist. Identification fields and values: Code=''.

What is AL Call Stack for error message?

• "No. Series - Impl."(CodeUnit 304).TestManualInternal
• "No. Series - Impl."(CodeUnit 304).TestManual
• "No. Series"(CodeUnit 310).TestManual
• Item (Table 27)."No. - OnValidate"(Trigger)

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Conclusion

Business Central 27 improves data integrity—but at the cost of upgrade surprises.
Fix the setup, fix the code, and never assume old behavior survives new versions.

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Regards,

Saurav Dhyani

https://www.youtube.com/@sauravdhyani