The use of SIA to record the ruling messages to be exchanged requires the registration on the FDF Portal with a CH-login. To do so, please click here. Please also activate the two-factor authentication. On the EFD Portal you can redeem your invitation code via the "Redeem invitation code" button in the upper left corner to get access to SIA.
If you already had access to SIA via myTaxWorld, please follow the instructions here.