The process to obtain the activity code for your company, in order to comply with the regulation of Factura Electrónica v4.3 is very easy.
The first thing you have to do is go to «Consultar la Situación Tributaria» in the link below,
Then select the type of your ID, if it is for a person (física) or for a company (jurídica), as corresponds.
Under the title «Actividades Económicas» you will find a table with the register activities and a column with the code.
Copy the principal activity code number and in Fygaro go to Settings > Electronic Billing:
Select the button "Add Activity Code" copy the number and click on Save.
If you have multiple activity codes you can click on the button of Add Activity Code and them select the Default for the principal one.