Income Tax Return

hi everyone.

i need someone to explain to me what happened. in january of this year. my monthly salary was higher by 30000. so, i was wondering why my monthly salary got increased (30000 yen) only in january? one of my friends said that you had "a tax return". I don't understand. so, when they return the tax, does it mean that:

1- they refused to take the income tax from my yearly salary because it's very low. which means I didn't pay my income tax at all
or
2- they have extracted/taken the income tax and returned some of it (3 man yen) it because my salary wasn't as high as they expected.

thank you.please answer.

I would say no.2.
Do you have salary slip to refer to on the breakdown?
Check your tax cut for the month and compare it to previous month.
Normally company will make final tax payment adjustment base on your total year income.

the company (the employer) withdraws the predicted income tax from your monthly salary. the company must do that by the order of the government. the amount is pre-fixed.
https://www.nta.go.jp/shiraberu/ippanjoho/pamph/gensen/zeigakuhyo2015/...
at the end of every year,
the company has to re-calculate your income tax on the base of your true income. (this means the company files employees' tax return instead of them.) generally speaking, the predicted tax, which was withdrawn already, is higher than the true tax in many cases. you will get some refund (by re-calculation).
most of companies pay the refund in December's salary. but, your company may pay the refund in January.

thank you so much guys for the explanation.
yes, i noticed that that company always withdraw between 25000 yen to 35000 yen for each month. so, when my monthly salary gets higher, they were withdrawing more taxes for the month as ken said.
i was surprised because someone told me that i have a tax return. i thought that i did not pay the Š“ΎΕIncome Tax for last year. according to ken, it looks that I paid the Š“ΎΕIncome Tax . Is that right?
one more question, how do they call the document that shows that I paid the Š“ΎΕIncome Tax in Japanese. is it called the Š“ΎΕ•[Hor Š“ΎΕΨ–Ύ‘? also, can i ask the company to give to me?
i want to give it to the immigration bureau when extending my visa.
thank you.

You will need to go down to the city hall
Taxation Department (Ε–±‰Ϋ zeimu-ka) to get the following for renewal/extension resident status.

Residence Tax Proof of Payment (Z–―Ε‚̉ېŏؖΎ‘ jūmin-zei no kazei shōmeisho)
Paper to confirm that you have paid your residence tax for this year.

Income Tax Certificate (”[ΕΨ–Ύ‘ nōzei shōmeisho)
Paper indicating your salary and how much tax is taken out.

Also you may require Proof of Employment (έEΨ–Ύ‘ zaishoku shōmeisho)be[] from your employer as proof of employment, depending on your resident status.

For extension period of stay application
http://goo.gl/JDQyY

Thank you so much for the information.