AIMZ mirrors the postings from the accounting system. What looks like the same invoice appearing several times under a production code (prod. code) may be several different postings on the same invoice number — each with its own ID from the accounting system.
Most common cause
The posting was first made to the wrong prod. code.
It was then reversed.
The correct posting was entered afterwards.
In terms of amounts, the reversal and the original posting should cancel each other out, so the forecast on the prod. code is not affected.
How to check
Turn on the System columns in the invoice table. They contain the information straight from the accounting system, including the ID and «System prod. code».
Compare the IDs. Different IDs mean different postings.
Look for warning signs. Lines where the prod. code in the accounting system differs from the prod. code in AIMZ are marked with a warning sign.
If you want to confirm what has actually been done, you can find the invoice history in the accounting system.
If it is a genuine duplicate registration, however, see Why does an invoice appear twice, and how do I check it?