afternoon train from rome to florence is a reservation mandatory

1) Do you want to pay full price or save money by buying ahead at lower prices?
2) If that particular high speed train is full will it derail your plans?

If you answered yes to either then go ahead and buy now.

Yes and Yes. Is there any specific train line that is better to book with? There are several. We definitely want the faster train.

The best train is any direct train scheduled when you want to leave that takes the shortest amount of time.
I would buy it today as the cheaper tickets sell out first

Before we went to Rome my sister checked the same route. Tickets were about $32 pp. she decided to wait. A few days before she wanted to go they were at $86 pp. she never went. But them now.

Look at trenitalia.com for train times, prices and to book. Make sure you don't miss the screen to choose your own seats. Your printout from that booking will serve as your ticket/s. Italotreno.com also runs some fast trains on that route, so you might want to check both sites

bm,

On the trip from Rome to Florence, you can use either Trenitalia or Italo Treno high speed trains, which make the trip in about 90 minutes.

Whether to buy tickets in advance or on the day of travel will depend on a couple of things....

• Can you commit to a specific train, date and departure time? The fast trains have compulsory seat reservations, so tickets can only be used on the ONE train listed on the tickets. If you board any other train by mistake, you'll be subject to hefty fines which will be collected on the spot.
• Are you really concerned about saving money on that trip or do you prefer more flexibility and spontaneity in your departure time?

As you're a group of four, one other point is that if you wait until the last minute to buy tickets you may not be able to get seats together.

Check the respective rail websites for departure times. If buying advance tickets, I normally use https://www.thetrainline.com/trains/europe . They sell tickets at the same price as the rail networks, sell tickets for both Trenitalia and Italo and sell tickets for many different rail systems in Europe (ie: one stop shopping).

Do you mean a reservation or do you mean buy a ticket?

If you buy a normal ticket, this includes the reservation. It will state date, time, train ID and your coach and seat numbers on the ticket.
These tickets are cheaper if bought in advance, you can buy them at the station on the day if you are prepared to pay the higher price.
You can check times and buy tickets on the Trenitalia site (this is the company that runs the trains): https://www.trenitalia.com/tcom-en
You must use the correct names for the stations (Roma Termini and Firenze S. M. Novella), NOT English translations.

If you have a rail pass, which is not the best option in Italy as the normal fares are cheap, then you need to buy a reservation as an extra purchase. Do this as soon as you are prepared to commit to which train you are travelling on.

Second-class tickets from Rome to Florence top out at 50 euros per person for full Base fare. Since trains run about every 15 minutes on this route, it's rare for them to sell out.

Laura is absolutely correct. Between 3 and 4 pm on a Monday there are five trains to Florence -- 3 fast trains. I am sure you can find one you like. The ticket will include a seat reservation that is specific to a train, date, and time. There are three levels of fares -- Super Econ, Economy, and Base. The first two are discount fares with restrictions as to refunds and changes and limited in availability. Once the discount tickets are sold out there will be only the Base ticket for that train. In addition you have both first and second class tickets. I see little advantage to first class tickets.