You are receiving the below error message when you are trying to publish invoices to your accounting package.
Invalid or missing Cost Code
This error is caused by missing or invalid information in the Cost code field of the invoice. If the Cost code is invalid, that would be due to a setting on it within your accounting software preventing it from being published to that supplier/customer account.
To clear this error, please do the following:
Unpublish the affected invoices.
Assign a valid Cost cost to that invoice from the dropdown menu.
Republish the invoices.
Please allow for a few minutes for the error to clear and the invoices to transfer over to your accounting package.