There are two types of tourist tax in Venice, a city tax is paid through your accommodation (as is the norm throughout Italy), and the new day-tripper tax (initially due to be rolled out in Jan 2023, but has been postponed to 2024) will be paid via an app for anyone entering the city. Prices will go up in busy periods, and fall in quieter seasons. However, if you are staying for more than one night you will be exempt from this payment.