Financial documentation about COE

Hello, I'd like to consult on something. I've been accepted to research student program at Sophia University while staying there with short term visa. After completing enrollment process, I submitted application form of certificate of eligibility. I only submitted the application form but today I found out that many schools require from applicants a financial documentation to verify financial ability in order to support themselves while studying in Japan which will be sent to immigration bureau along with COE application form. But there were no warning about it on guideline and the lady at student affairs didn't warn me about it neither. So I wonder if it's an obligatory document for all schools or not?
P.s: I paid school tuition as cash

If immigration needs something else, they will let you know.

I see, thank you. I'm kinda relieved now