IMU - have the categories changed?

For altri immobiliare they mean seconda casa etc. You need to put your prima casa (whatever category it is ) in the first box. I guess they think it is obvious that to be your abitazione principale it has to be an A/something.

Careful! Last year they made some slight changes. We saw that in our case. Two years ago, we submitted new planimetry and had records modified, as the previous owner had carried out renovations which had not been reported. The first year, we expected some changes in the category and this happened. This year, we only expected a further increase in the "rendita cadastale", but we also got an adjustment of category. We were told that we could challenge the decision, but the difference does not warrant it. Besides, the Comune needs the extra revenue....

Thank you Penny and Gala.  As ever you have come up with great advice.  You are right Penny because when I clicked on the first category - prima casa - and then scrolled down to the bottom of the page there was the calculation in tiny font and it was the same answer I had originally worked out.  I haven't changed the house since it was built 5 years ago Gala so will still be in the A2 category but I can see that others might be affected.

Yes, you can have one garage/box included as coming with a prima casa, but then you can have another building too.  So on the website, you have prima casa (A something) wiht hte possibility to have a pertinence included (a garage, a cantina, a chicken coop etc)  OR you can choose altri immobili (property where you are not resident) and other stuff that could never be 'prima casa' - office, church etc ....  So for example - take your act of sale and tot up the rendita catastale of all your particelle (house, garage and cantina) and put them in the box with an A something rating and add your deductions. If its a second house, you will have to calculate your house, cantina and garage separately as they all have different co-efficients, and then add them up, divide by two (for the tranches) and then divide by 2 again (half to the comune, half to the govt) - easy? Not. 

Thanks everyone.  It was just the way that the first choice from the side drop down menu did not use the classification A which confused me - instead it had "abitazione principale" and the C categories I mentioned above.   All sorted now.  No separate pertinenze as the garage is underneath and no outhouses, chicken sheds, rabbit hutches nor moats with duck islands etc (joking!)