Rome, August 19 - Italy's latest weapon against tax evasion, the so-called "redditometro" or "income-metre", became operational on Monday. The database cross-referencing software compares household spending to income declarations, mining information going back to 2009. Consumption deemed inconsistent with declared incomes will trigger checks by tax authorities, and taxpayers will be required to justify their spending capacity. The Italian tax revenue agency is allowing a "tolerance" level for household spending of up to 20% over calculated spending capacity before triggering an audit. The new measure was dismissed as ineffective by a Venetian small business association. The new instrument this year could add 815 million euros to public coffers, or 0.7% of total funds lost to tax dodging - estimated at 120 billion euros per year - according to the CGIA of Mestre, a small business association based in a mainland zone of Venice. "The tax authorities will recover only small change," said CGIA Secretary Giuseppe Bortolussi, who added, "honest taxpayers have nothing to fear".