You may be asked to supply a statement of income for the financial year (gensen-choshu-hyo 源泉徴収票 ) when you are filing a tax return in your home country. In Japan these are usually sent out in January for the previous year of January 1st – December 31st.
Although other JETs on the same contract year as you will have the same base salary, your take home pay will be different due to a number of factors – nationality (different rates of Japanese National tax), municipal tax. Therefore, you most likely will be filing for a different amount of tax than your co-JETs.
For 2020 incoming US-JETs, welcome to the compulsory-tax-party. The tax agreement allowing US-ALTs to avoid paying Japanese income tax for a maximum of 2 years has come to a halt. If you are one of the lucky ones who already submitted the necessary forms in either 2018 or 2019, consider yourself lucky. You are one of the final JETs who has the privilege of dodging tax payments. Enjoy.
For the US-JETs needing to file a tax return, have a look at the in-depth guide the Kumamoto JET’s have put together. https://kumamotojet.com/reiwa/u-s-tax-guide/
To the JETs from everywhere else on the globe, your country will most likely have an international tax law stating you will need to pay taxes in your home country as well as the country you are residing in – for us, Japan. However, some countries, like New Zealand, may remove your ‘tax payer’ title after you have been out of the country for over a certain amount of days. This does depend on your financial ties to the country like, student loans, owning a house, national income etc. Your best bet is to keep yourself up-to-date by checking out your government official website. They should have the answers to all your queries.
The Kyoto JETs have put together some information for JETs from Australia, New Zealand, Canada, Ireland, United Kingdom and South Africa. https://kyotojets.weebly.com/home-country-taxes.html