Managing the business documents in a well-organized way is a key factor in any business. The numbering method is an important aspect in this area. One common methodology is to assign a separate numbering series for each document type, such as order, delivery, invoice, etc. This is the default option in SAP Business One. But there is another way.
For example let’s say that your business prefers to create all the sales documents under one numbering series and all the purchasing documents under another numbering series. For such scenarios SAP Business One provides you special settings.
Before posting any document or transaction, select the “Permit More than One Document Type per Series” checkbox (in Administration > System Initialization > Company Details > Basic Initialization tab). Note that this setting is irreversible. Now, define the required numbering series in ‘Document Numbering’ window. In the “Relate Series to Document” window you can assign the relevant series to the respective document types.
This function applies also to master data records and is available in SAP Business One, version for SAP HANA and SAP Business One.
Source: Ari Schapira | SAP Business One – The Tip of the Week