Number series: set them up right from the start

Number series control how documents and master data are numbered in Business Central. They are often set up at the last minute and changed afterwards, which can cause gaps, duplicates or unexpected numbers. The article goes through how number series fit together, what you need to decide for documents and master data, and what to do at year-end. There is a checklist at the end. It is written for both finance and IT.

Code, lines and documents

A number series consists of a code and at least one line. The line specifies a starting number, an ending number and a starting date. You can have several lines per number series with different starting dates, so that a new line takes over when the date is reached.

You can also set a warning number, so that the user is notified before the series runs out. It is a cheap way to avoid a stop in the middle of invoicing.

For documents such as sales invoices and credit memos, there are often legal requirements for consecutive numbering. Check your auditor's requirements and the rules that apply with your local tax and company authorities before you choose anything other than consecutive series.

Many choose separate series for each document type, and preferably a prefix that shows the type or year. Posted documents can have their own series, so that order numbers and invoice numbers are not confused.

Master data

Customers, vendors and items get numbers from number series, but here consecutive numbering is required less often. Choose whether the numbers should be meaningless or carry information. Meaningless numbers are easier to keep stable.

If you migrate data from another system, you need to decide whether the old numbers are kept or replaced by new ones. If they are kept, the number series must start above the highest old number.

Gaps, year-end and checklist

Microsoft Learn describes a setting on number series lines that allows gaps. It uses number sequences behind the scenes and can give better performance because there is no locking. Use it only where there is no requirement for consecutive numbers. Read the guide on creating number series for the details.

Consecutive series can block when many people post at the same time. That is the price of an unbroken sequence.

If your series has the year in the prefix, you need a new line or a new series for the new year. Set it up in good time, and test in a sandbox that the first document in the new year gets the right number.

Also check fiscal years and periods, so that posting dates are allowed.

Use the list when you set up number series for the first time.

One series per document type, with clear prefixes.
Starting number above any migrated numbers.
Warning number and ending number with plenty of room.
Decision on gaps per series, justified by legal requirements.
New line or series ready for year-end.
Permissions, so that only a few people can change number series.

Who may change them

Give only a few users permission to change number series. A series changed in the middle of the year can create duplicates or gaps that are hard to explain to the auditor. Set up a fixed procedure where changes are agreed, documented and tested in a sandbox.

Number series lines can also be used by apps and extensions. Ask your partner before you change a series that a customisation may depend on.

Testing and documentation

When you copy an environment to a sandbox, the number series are copied with it. The series in the sandbox are separate from production's, so posting in a test does not change production's counters.

Use test companies with their own series, so that test documents cannot be confused with real ones.

Write a short overview of all number series: code, purpose, prefix, range and whether gaps are allowed. Keep it together with the rest of the setup documentation.

The overview is useful at audit, when a new employee needs to learn the system and when a consultant has to troubleshoot a posting that stops.

Help with setup

Addverk is a new Business Central partner. See our implementation service if you want help with the setup.