Hi @Penns
You may wish to refer your developers to this guide which has a breakdown of the supported fields for the invoice: Importing sales and purchase invoices
An Excel spreadsheet isn’t by default a CSV format, but it can be saved as one. When viewing the file, if you go to File >> Save As, you can then select “.csv” as the file format.
However, if you’re asking your developers to make some changes, perhaps it’s worth looking at the option of linking your account with our API, which could do this process automatically for you. More info here: https://api.quickfile.co.uk
Are these sales or purchase invoices? If they’re sales invoices, there may be another way to do it too.