Setting Default Series 
When you have defined all the required series, you can set a default series for each group of series.
Note
For the document series, to make sure that document numbering can start immediately, the application automatically generates the Primary series with default settings for each document type. You can change this primary series to meet your needs before you start to create documents.
The Document Numbering - Setup window displays only the default series. Before you make any changes in this window, make sure that you review the list of series of relevant master data or documents by double-clicking the row header.
You can change the value of the First No. field of a series until the first business partner, item, or document is created within that series. Once the first business partner, item, or document is created, you can no longer change the value of the First No. field, but you can still change the value of the Last No. field. Nevertheless, you have to verify that the changes do not result in overlaps with other series. Information such as remarks, the assignment of default series to a group, or the lock can be changed even after master data or documents have been created.
Procedure
When the Permit More than One Document Type per Series checkbox in the Company Details window is not selected, you can define a numbering series as the default following the steps below:
From the SAP Business One Main Menu, choose
Administration 
System Initialization Document Numbering 
. NoteTo sort a column in this window, double-click the column name. The column is sorted in ascending order. To sort the column in descending order, double-click again. In the Chile and Mexico localizations, you can sort the first column only.
End of the note.Double-click the row header of the master data or document for which you want to define a default series.
In the Series - <Document> - Setup window, specify the group to which the series that you want to define as the default belongs.
Select the series and choose the Set as Default button.
Specify which users should use this series as their default.
Select the Set as default for certain users option if you want to set the selected series as the default for a specific set of users, for example, the employees of a department. You are then prompted to select the relevant users.
To confirm your entries, choose OK.
NoteYou must make sure the users specified are authorized to use the group of series. For more information, see Authorizations.
End of the note.In the Series - <Document> - Setup window, choose Update and OK.
In the Document Numbering - Setup window, save your entries by choosing Update.
When the Permit More than One Document Type per Series checkbox in the Company Details window is selected, you can define a numbering series as the default following the steps below:
CautionSelection of this checkbox is irreversible.
End of the caution.From the SAP Business One Main Menu, choose
Administration System Initialization Document Numbering Relate Series to Document
. NoteTo sort a column in this window, double-click the column name. The column is sorted in ascending order. To sort the column in descending order, double-click again. In the Chile and Mexico localizations, you can sort the first column only.
End of the note.Relate the required series to the master data or document for which you want to set a default numbering series. For more information, see Relate Series to Document.
NoteIn the Numbering Series - Setup window, make sure the series you want to set as the default is assigned to the appropriate group. For more information, see Defining Additional Numbering Series.
End of the note.Select the series you want to set as the default and choose the Set as Default button.
Specify which users should use this series as the default.
Select the Set as default for certain users option if you want to set the selected series as the default for a specific set of users, for example, the employees of a department. You are then prompted to select the relevant users.
To confirm your entries, choose OK.
NoteYou must make sure the users specified are authorized to use the group of series. For more information, see Authorizations.
End of the note.In the Series - <Document> window, choose Update and OK.
In the Relate Series to Document - Setup window, save your entries by choosing Update.