Clashing Paid Invoice Numbers

[XN-Matt]

We've seen clashing invoice numbers when using sequential invoice numbering.

This occurs when WHMCS gets two payments at the exact same time and it assigns the paid invoice number to the same invoice. This wasn't something we were aware was happening as we were bulking transactions to copy to a third party accounting software. Now that we automatically sync these daily, we were getting some nasty errors to find this was the cause.

WHMCS should never create a duplicate invoice number or paid invoice number.

Support didn't really give much support or options. It was explained that because WHMCS does not support transactions, they cannot fix this easily or soon. They seemingly shrugged off as this problem only occurring under a "very specific set of unusual circumstances". I wouldn't consider two customers making payments at the same time "unusual" nor that we get two IPN notifications from PayPal at the same time, unusual, especially when they have backlogged IPNs.

Their only other suggestion was to turn it off which would then take sequential invoice numbers and change them randomly to the base invoice number. Certainly not an option or something our accountant will be happy with, let alone the tax office.

If they had given this warning, knowing it could have happened due to the lack of proper code and testing around it, we wouldn't have ever used it but still, to date, no such warning in their documentation.

Would love to hear if anyone else has been impacted by this, dare I say, if you bulk your transactions at the end of the month to your accounts software, you might not even know.

[dataforge]

We have an issue with whmcs creating invoices with duplicate invoice numbers.  I am not sure at what point it does this, I sort of thought it was an issue with my addon that syncs whmcs to my quicbkooks online.  I have never figured out a pattern, but I right now have an invoice that was made like 2 years ago, and a new invoice for a different customer that was made just last month and they both have the same invoice number.  I keep getting errors from my addon on invoices not syncing to qbo, and the reason is it wont send an invoice with a duplicate invoice number already in qbo.  I have no suggestions for either of us at this time.

[XN-Matt]

Sounds like the same issue but in typical WHMCS fashion, it's just not important enough despite the fact that there is a large flaw in invoicing and payments.