Most people in Italy have to fill in Tax returns, many do it themselves, many use a commercialista to file the returns. If you work for yourself, so self employed an artisan, a baby sitter and so on, you will need to have a Partita IVA a personal tax code.
In order to declare income, the taxpayer can file Dichiarazione dei Redditi or Modello 730 (Mod. 730, a simplified income tax return) on the basis of specific tax rules.
Mod. 730 In Italy, the Mod. 730 is a simplified income tax return.
It can be filed only for specific incomes (i.e. incomes subject to ordinary taxation) and the taxpayer must meet the following conditions:
Individual is an Italian tax resident in the year of filing of the Mod. 730 and in the previous one.
Individual has a withholding agent in Italy in the period of the filing of the Italian income tax return.
Individual has no VAT number.
The main advantage of this tax return is that the taxpayer is not obliged to prepare any calculation; the balance resulting from the tax return is directly withheld or refunded to the employee in the Italian pay slip. Married couples can file the Modello 730 jointly. This tax return has to be submitted to the Italian tax authorities by 30 September via electronic filing.
You have to file taxes yearly, any social security contributions are deducted from any tax due, so you are not paying double the tax.
In case Mod. 730 is not applicable, the taxpayer has to file the Italian tax return called Dichiarazione dei Redditi. This tax return has to be submitted to the Italian tax authorities by 30 November via electronic filing. Married couples cannot file the Dichiarazione dei Redditi jointly.
On employment income, the employer, as tax agent, effects a monthly withholding tax on the basis of the tax rates applicable to the annual employment income. The employer is obligated to issue within 31 March of the next year an annual employment certification, so called Model CU, certifying the amounts of the taxable income of the employee and the withholding taxes operated during the fiscal year.
Most things are done by a commercialista. I found when hunting around finding one that speaks English is hard, so I looked for other options, one I found was an app that also has a web portal, where you submit everything online or via the app and record your income and expenses. This way is easier because you can use google translate if need be, if your Italian is not the best.
You get €10 off the annual fee, which starts at €169 but also includes the opening of your P.Iva in the first year.
(This is not tax advice, this is just some information on how the system works)