To have tax residency in Italy it is necessary to reside for at least six months during the year. Consequently, since September falls to you for the fiscal year 2021, you will be resident abroad, regardless of whether you return your residence to Italy at the time of the transfer. Therefore, you will have to continue to pay taxes in France, indicating in the tax return that you will present next year also the income received in Italy and the taxes applied, in order to be able to take advantage of the regime against double taxation that allows you to deduct from taxes owed in France for those already paid in Italy. Starting from the tax year 2022, that is, from when you are fiscally resident in Italy, your employer is required to apply the subsidized tax regime for repatriated workers. For the application of the subsidized regime it is mandatory to submit a written request to the employer, otherwise it cannot be recognized. So you will necessarily have to submit the application and the employer will certainly be able to apply the subsidized regime, which has been in force since 2015. The rules introduced since 2019 have simply broadened the scope of its application.