In Elorus, you can create your own series for sales documents and estimates by selecting Settings -> Document number series or Estimate number series -> Add.
Every series, is designated as a unified serial numbering regardless of the document type. When you enter a new series on the application, you also define the document types to which it applies. You have to set at least one type of documents for each series.
To apply a numbering series in your documents, you need to select is from the Number field.
Suppose that you created series “A” for “Invoice” and “Credit Invoice” document types. The first “Invoice” you publish will receive the numbering #A-1, while the next of the same series will receive numbering #A-2, even if it actually is an “Credit Invoice”.