Duplicate Invoice Number Error

When uploading a new Invoice from the fmAccounting Link (QuickBooks Online Edition) file you might encounter the following error:

{
"Fault": {
	"Error": [
		{
		"Message": "Duplicate Document Number Error",
		"Detail": "Duplicate Document Number Error : You must specify a different number. This number has already been used. DocNumber=1012 is assigned to TxnType=Invoice with TxnId=145",
		"code": "6140",
		"element": ""
		}
	],
	"type": "ValidationFault"
	},
	"time": "2023-03-19T23:18:22.638-07:00"
}

QuickBooks Online doesn't allow the creation of a invoices with the same invoice number (DocNumber field). You will need to modify the value in the DocNumber field and then upload the Invoice again (the DocNumber field is set to auto-enter a serial number and cannot be modified by default so you might need to adjust these settings to allow another value to be entered into this field). You can get more information about the options for generating the DocNumber when uploading to QuickBooks Online here.

You can read more about how QuickBooks Online generates the DocNumber value and how to allow duplicate DocNumber values by including an additional query parameter here.