Is it right that IMU+TARI+TASI should

Well the IMU and TASI can be put together, but the TARI (rubbish tax) is a different calc. If you have not already seen this site, then it may be a good idea to calculate your own tax on your house.

Thank you very much! I was confused, because some sites assert, that the sum of all three taxes should be no more than 1.06%.

TARI is separate and calculated on the size of your property. The other two are based on catastal value and the legal maximum is 1,06% of the revalued catastal value.

I don't think it is as simple as that. I'm not an expert but you'll see from the website for calculating the IMU and TASI that there are hidden coefficients. I think that there is a general 5% revaluation of the valore catastale and a further 160% increase for residential properties (less for land and some other classes of property). So your combined IMU and TASI is likely to be about 1.45 (at least in my case) of the basic valore catastale.

My apologies! I've just re-read the original question and you have understood this.

I think the tax preparer for this situation is the right choice since there are many cases related to tax report should be done.

You can find more details at white pages of individuals which give you good ideas about how to get personal usages properly. Hope this can help you solve out your problem.