Read more about Exporting Invoices and changing the Export Format.
Spoonfed allows you to Export Sales Invoice information (in an .XLSX format) for importing into Sage (Desktop or Client/Server version).
The import will update your Customer Ledger Account, the Income Account and, if applicable, the Sales Tax Liability Account in Sage.
Change Format to Sage Line 50
To set your Spoonfed to produce the Export document in the required Xero format, go to Setup > Organization > Invoicing > Account System 'Sage Line 50'.
If your Customer already exists in Sage, then the Customer Code in Spoonfed must exactly match the Customer Code in Sage. If no exact match are found, Sage will create a new Customer. This will lead to more than one account for the same Customer in Sage and result in confusion.
It might be a good idea only to create new Customers in Spoonfed, that way you won't get multiple accounts being created.