The returns come out of your journal, not out of a side spreadsheet.
It comes from the general journal, box by box. You sign it on your own computer, with your certificate.
The returns are not filled in by hand: they are computed by walking your journal for the period.
The app generates the official fixed-length file the tax office expects, and you sign it on your own computer with AutoFirma, so your digital certificate never leaves your machine. Once filed, the period is locked.
You do not have to switch everything on. Tell us how you work and we will tell you where to start. ATAZEL is in testing: write to [email protected].