“Our customer has yet again sent us two orders with the same number. One has 15 lines and the other has 10 lines. How should we know which one is correct? They even have the same dates”, worries sales assistant Maria. “I know, and even calling them and asking about it will be difficult, as how to even distinguish between them?” agrees her colleague Kaspar.
Prohibiting duplicate numbers for documents is one of the pillars of well-built information systems. Reusing document numbers can cause not just confusion and waste of time, but serious errors in fulfilling orders and delivering wrong quantities of products.
In most software applications, a document number is considered a primary key (primary identifier), so it has to be unique and could not be duplicated. There are also programs where the document number might be a secondary key, and then some additional field is used for distinction, such as using a sequence number or similar.
However, even if your software allows duplicate numbers, this can cause issues for both you and to your partners:
- Accounting – Both GAAP and IFRS say that document numbers should be unique. This also makes auditing easier. Otherwise, when an auditor sees a lot of duplicate documents, it may prompt them to look for other accounting irregularities, and spend considerably longer time in the process.
- Sales – sending several documents with the same number would lead to duplicates. The receiving party would have no basis to know which copy is correct. This uncertainty in real life would result in calling or e-mailing the sender and solving this problem by asking. And all this would mean delays in the supply chain process and final sale of the product. In the worst case, it could lead to out-of-stock situations; making the supplier, the retailer and the consumers all unhappy.
- Reclamations – In case of conflicts, there is no way to prove which document was “the original/correct” one. It would also be impossible for the service provider to help the conflicting parties as also in document log there would be multiple copies of the same document.
When the first document you sent to your trade partner was erroneous, never send a new one with the same number. Best practice is always to create a document with a new number and clearly indicate that the previous one was incorrect. In case of invoices, this is by law done via credit invoices.
The good news is, most ERPs have a simple functionality of creating both credit invoices and new invoices as copies from old invoices. Following the best practice you will have a much quicker and better process to handle problems, might any arise.