Every finalized document receives a unique document number. The document number configuration determines how these numbers are built — prefix, suffix, mask, and counting sequence — and which documents share a sequence, so your numbering fits your accounting setup without manual intervention.

To configure document numbers, navigate to: Configuration > Billing > Document Numbers. The page consists of three sections.

Step 1: Select the numbering strategy

In the Document number strategy selection section, two settings control the overall behavior. Both can be edited.

Document ident source

Determines where document identifiers come from — for example Generated, where instellix generates them itself.

Active document number strategy

Determines which numbering approach is actually applied when a number is assigned — for example Rule based, which uses the counters and strategy rules configured below.

Step 2: Configure document counters

A document counter is a number sequence. The Document counter configurations table shows each counter with its ident, prefix, suffix, mask, starting value, upper limit, and Last document number — the number most recently drawn from that counter, which lets you monitor how far each sequence has progressed. When creating a counter, the following fields are available:

Document counter ident

The unique name of the counter (for example GLOBAL). Strategy rules reference counters by this ident, so choose a name that tells you what the sequence is for.

Prefix and Suffix

Fixed text or placeholders added before and after the number — for example the prefix ##YEAR_SHORT## embeds the two-digit year, making the issuing year visible in every document number.

Document counter mask

Shapes the format of the generated number itself. Placeholders such as ##YEAR##, ##MONTH##, or ##DAY## are resolved when the document is created.

Document counter reset

Determines when the counter starts counting again — for example at the turn of the year, so you can run year-based sequences, or manually.

Document counter lower limit / starting value

The first number the counter assigns.

Document counter upper limit

The highest number the counter may assign. Size it generously for your expected document volume.

Step 3: Define which documents use which counter

The Document number strategy configurations section decides which documents share a number sequence. It offers four tabs:

• Default — one tenant-wide configuration. Here you set the Fallback counter ident (for example GLOBAL).
• By document type — separate sequences per document type (for example invoices vs. credit notes).
• By billing group — separate sequences per billing group.
• By service country — separate sequences per service country.

Within a configuration you add rules. Each rule points to a Document counter ident and defines when it applies using the criteria Billing Groups, Document type, Customer type, Operating Sites, and Tax location. The rules are listed in descending order of priority: the first rule that matches a document determines the counter. To change the priority, use the edit icon and reorder the rules via drag and drop.

Via API

Counters and strategies can also be managed via the Document Number Configurations endpoints: create a counter · select the active strategy · create the default strategy or strategies separated by document type, by billing group, or by service country.