Spouse visa - tax declaration?

So, I am thinking about moving back to Japan (yeah, I like it in the end :) )
Me and my girlfriend are planning to get married, and I will obviously apply for a spouse visa to stay there.

My question is, do they require a tax declaration upon submission?
That might be an issue for me. I am a student who only works part-time and don't earn enough to file a tax declaration (for my country, you don't have to do it under 5k euros per year). Will that be a problem?

My girlfriend has a stable job for about 250 000 yen per month, her family has a business so they could eventually be guarantors.

Any ideas? Could the immigration refuse a permit because of it?
At any rate I work online and am planning to extend to full time once I will be there, I wonder if that is possible?

Only immigration can answer your questions and inform you the requirements.
Ask your girlfriend to contact the local immigration office.

http://www.immi-moj.go.jp/english/tetuduki/kanri/shyorui/20.html

Documents proving your relation based on which your visa will be granted, such as Marriage Certificate, Birth Certificate, Family Registry (Koseki), Resident certificate (Juminhyo)...
Letter of Guarantee
Questionnaire (for Spouse of Japanese national)
Documents to prove your income (Certificate of employment and the most recent tax payment certificate). If you don't work, you will need such documents from the person who supports you financially, or other documents such as your bank statements showing enough savings.

Thank you! :)

they dont need your tax .. as long as you have not been living and working in japan.
but your spouse will provide her tax and other documents as your gaurantor in japan.

That's great, thanks for the info! :)

Anyone have any idea how much "enough savings" is? Curious for myself.

Anyone have any idea how much "enough savings" is? Curious for myself.

I am curious about it too :)

Curious fact: my girlfriend called the immigration office yesterday, but they told her I do not need to provide any income proof? Odd, maybe the employee just wanted to go home, it was past 4pm in japan, though it would seem very odd to me

I'm not sure where justmyday got their information (the posted link is about notifying changes and not about applying), but as far as I know only your wife (or a guarantor) will need to prove sufficient income, like chike20 said, because immigration wants to ensure they can support you. Since you will no longer have your previous job when you move to Japan, it's completely irrelevant what you used to make.

In any case, don't take advice here too seriously and instead listen to what the immigration officers tell you.

if you are working in Japan, you have to show some document which prove your income.
if you are not working in Japan, you don't need to show such a document, because immigration has now way to confirm your foreign income. (they will not consider your foreign income, even if that is huge.)
you (you and your wife) have to show that you have enough income to live as a family.
if your wife's income in Japan is not enough, your wife's parents (living in Japan) can be financial guarantors (the parents have to provide official income documents).
if the combined incomes of you, your wife, and wife's parents are not enough, you have to find additional guarantors (relatives), or they will refuse to issue the visa.

That's clearer, thank you for the help! :) It makes sense
I also emailed the immigration office just in case, to have something written and avoid confusion

Thanks!