If you work in a Japanese company...?

Based on what I know, bonuses are based on its company's performance and not based on the performance of that particular individual. Usually bonuses for winter time is larger than summer bonuses. It is approximately twice to three times as much as the monthly salary. However, unlike the western society, Japan focuses on group effort and therefore individual's effort or performances are not highly valued. If the company is doing good as a whole, bonuses also rises and if it isn't, bonuses decline as well. My co-worker once stated that his friend's bonus was reduced to null due to this economic recession. Unlike the American company bonuses are for every one when the company is doing okay. However, if you are working for the Gaishi(foreign capital) Firm in Japan, system could be bit different and not everyone in a company receives bonuses. It is only for the top people.

It depends on each case.

In fact, bonus is something which changes every year. So there is NO general answer.

Usually, you can get 2 months of your salary both in summer and winter at average. So you can get the amount of 4 month salary in 1 year. It depends on each company. We can say that we can get 1-3 months at one time generally in Japan.

But even in the same company, bonus amount often changes year by year as its performance changes.

I think few labor contracts "fix" the bonus amount. So it really changes year by year.

I work for a Honda supplier and we get one month's salary for our bonuses. However, I have heard from some friends at Honda that they get 3 months! So I think between one and three is a safe bet.

My guess is you will get a months pay each bonus season.