Let us simulate the same scenario.
I have created a new no. series named ‘Test’ with a starting document no. ‘TEXT0001’ and assigned it to both ‘Unposted Sales Invoice’ as well as the ‘Posted Sales Invoice’ in sales & Receivables Setup window.
Afterwards, we have created 2 unposted sales invoices with the document no ‘TEST0001’ and ‘TEST0002’ (generated by the no. series Test).
The first sales invoice has the external document no ‘ABC’ and the second one has ‘ABC1’ as external document no.
Now what will happen if I post these documents? One of the comments in this discussion says that it will create a document no after the last no created by the no. series. So the first posted document will be ‘TEST0003’? What do you think? Let me post the invoices.
To make it more interesting, I have posted the second document (‘TEST0002’) first and the first document (‘TEST001’) second. Here is the screen shots of the posted documents. You can identify the documents with their respective external document no.
This is the first document posted second identified by the external document no ‘ABC’.
This is the second document posted first identified by the external document no ‘ABC1’.
You got the answers?
In this scenario, the posted documents are taking the same document no assigned in their unposted state. And as no new no is generated by the no. series, the posting process does not update the ‘Last no used’ field of the no. series line.
Have you tried this ever? Try it and I believe you will also find application of this functionality in real life implementation scenario also.
Best of luck