[jaclaz]

Well, in that case you are a final customer, should you put on an online service allowing customers to book and pay for dinner in many different restaurants it would be different.

In Italy it is a rather common occurrence in different fields to be required by Law to act as "sostituto d'imposta" (loosely translatable to "tax substitute", the real translation should be "witholding agent"), as an example banks when you pay through them certain types of services, or hotels when you pay the "city tax" for your stay, or firms hiring a consultant.

The taxes are witheld and then paid directly to the revenue service (periodically), the idea is that instead of receiving millions or billions of small payments, the state receives much less larger (cumulative) payments.

If we take as an example the city (tourist) tax, each customer should pay (say) 2 Euro for each night they stay in a hotel (or AirBnB), a (fully occupied) hotel with 200 beds would generate 200 small payments, 2 Euro each, per day, instead the hotel collects them (in name of the state) and pays in a single instance every three months, so instead of 3x200x30=18,000 micro payments, only one payment/transaction is generated.