In Reckon, GL Codes are called Chart of Accounts and you can export them in much the same way as your Suppliers.
- click on File > Utilities > Export > Lists to IIF Files …
- from the Export dialog select Supplier List and click OK
- save your Supplier data to a file called Suppliers.IIF
- go to the Admin tab and click Supplier Cards set-up
- use the Browse… to locate the Suppliers.IIF file you created above
- click on Upload
Your Supplier data has now been successfully imported into invitbox.