Fellowship

Usually all candidates admitted to a SISSA PhD program are awarded a fellowship. The fellowship exact gross amount can change from time to time (usually it's increased) but at the end you'll get (around) 1000 euros per month. For 2009 the gross amount is 13350 euros and each month a PhD student gets 1020 euros net per month.

Your fellowship is considered by Italy a tax-free income hence your personal income in Italy is - considering only this fellowship and the other contributions from SISSA, that are not regarded as tax free in principle - so low that you don't reach the income threshold required to pay taxes in Italy.