In Microsoft Business Central, this error often occurs when posting journal entries. Let’s look at why it happens and how to fix it.

Why is the error thrown?
The error occurs when you try to reuse a Document No. that has already been used in a No. Series that doesn’t permit duplicates. In the video below, I demonstrate the error while working on a two-line journal, so let’s get started with the setups and situation. For more information on setting up No. Series click here.
- General Journal Batch: The batch in my example has the No. Series code GJNL-GEN, which will automatically generate Document No.s as I create lines. Business Central checks the last number used in the No. Series setup to determine the starting number of the journal.
- No. Series Setup (GJNL-GEN): The last number used was G00005 and I have G00002 on my journal lines. I can’t use G00002 again because I’ve already posted journals with it.
- This raises a question. Why are my numbers prior to the last used? The answer is that multiple batches can share the same series, leading to duplicates. If two users create new lines in different batches with the same No. Series, both will start from the same Last Used No.. The first batch to post will succeed, but the second will error because the numbers are already taken.
- Common Misconception: Users often think that enabling Allow Gap in Nos. will let them type the next number, but that’s not true. This issue happens only when Manual No.s is off for the series, meaning you can’t manually enter the latest number.
Three Possible Solutions
- Define a Posting No. Series (Recommended) : Maintain your existing No. Series for auto-filling Document No.s, even with the potential for duplicates across journals. Create a new No. Series and assign it to the batch in the Posting No. Series field. When the journal batch is posted, the document numbers will be replaced by the next number from the posting number series and assigned to all ledger entries. This method requires Manual No.s to be enabled for the batch No. Series.

2. Before posting, select the Renumber Document Numbers button of the journal. This will update the journal numbering to use the latest numbers from the assigned No. Series.

3. Turn on Manual No.s: This will allow duplicates to be used alleviating the error. For help with that setting, please click here.
Thank you for reading, I hope you learned something new.
As always, stay SAASY my friend.
-Dino



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