Number Series
Every document gets a number from a series. Series are created during setup, one per document type.

How numbering works
Section titled “How numbering works”A series has a prefix and a running counter — for example SINV- followed by an incrementing number. The next number is assigned when a document is created.
Numbers are not reused. Deleting a draft does not return its number to the pool, so gaps in the sequence are normal and not a sign of missing documents.
Changing a series
Section titled “Changing a series”Set which series a document type uses by default in Settings → Defaults. You can create additional series and pick between them on a document where more than one exists.
Starting from a specific number
Section titled “Starting from a specific number”If you are moving from another system and need to continue an existing sequence, set the series counter to the last number you used. New documents will carry on from there.