This error usually appears when one tries to create a portable company fie or when going for the Direct Deposit option for sending the paychecks. If you are getting this issue on your software then here are the methods to fix QuickBooks Error code 31600. Thus, read this blog all to the very end.
Read More:

Open QuickBooks and navigate to the "Help" menu.
Select "Update QuickBooks."
Click on "Update Now" and ensure that the "Reset Update" box is checked.
Click on "Get Updates" to download and install the latest updates.

Regards,
Peter