reserved seats on Japan Rail

Hi everyone,I have read here that you can get on the reserved section of train (when it's crowded on the unreserved car) and pay for it on board train. My question: I will be getting a JR pass. Do i have to pay extra if I did not reserve a seat but somehow the unreserved section is crowded and I choose to get a seat on the reserved car? Thank you for your time.

The JR Pass allows you to reserve seats for free: allow the time to do it at the ticket office before your train departure time: its so worth it:

No you don't pay, however you need a seat reservation before you get on board.

For example you can't go into the unreserved section, see if it's busy then move to the reserved section, you need a reserved seat before you enter the train.

While the seat might look empty, it might fill up at the next station or down the line.

NOW sometimes, the conductor might let someone do it, other times no.

Thank you for your replies. (1)What is the minimum time needed to reserve a seat? (2)What happens if I miss the train that I've reserved (I will have a JR pass)?

Moonges,

(1)What is the minimum time needed to reserve a seat?

You can reserve seats right up to the time of departure, but of course you need to allow a few minutes to get from the ticket office to the platform. If the ticket office is busy, it can sometimes take as long as 10 minutes.

(2)What happens if I miss the train that I've reserved (I will have a JR pass)?

There is no penalty or anything, but it means that someone else may have to stand despite there being a vacant seat, so you should make the effort to catch the train you are reserved on or else return the unused seat reservation to the ticket counter so that the seat can be released for someone else further down the line.

(1)What is the minimum time needed to reserve a seat?

I am not sure whether I understand your question correctly. If there is no line up, you succeed to get across your order very quickly and it is a straight forward order, the whole process could theoretically be completed within one minute.

What happens if I miss the train that I've reserved (I will have a JR pass)?

Then, your seat will remain vacant, which could cause some minor inconvenience to other travelers and the railway company. As for yourself, you will have to make a reservation for another train or ride in the unreserved section of any other train.

I think it is best not to miss the train that you have a reserved seat. Note that the reservation is free at the moment.
I am unsure if one can cancel the reservation before the train journey starts.

It is certainly better to not miss the train with a reserved seat: if this happens often enough the valuable "free" reservation option may well disappear from the JR Pass.

It is possible to cancel reserved seats before departure: we arrived earlier than expected for a transfer and were able to cancel the seats we had and obtain seats in the earlier train at a moments notice, with about 5 minutes to spare: don't recommend cutting it that fine but it worked for us at the time (heading home from Narita: managed earlier NEx transfer at Shinagawa)

If the unreserved section/cars of a JR train is full or very crowded, there is a good chance the reserved section/cars will also be full. If not in a rush and the text train is less than half a hour away, maybe better to wait for that train and be near the front of the line for a good/better seat.

Thank you everyone. I understand how the system works now. :DDD