do you have a bill that indicate where service is provided? for example I pay my sister's internet. the bill gets mailed to me, but on the bill it lists her address as the place where service is provided.

*indicates

^^ yea they usually do some kind of utility bill

see the problem is our utilities are shared between our house and the parents in law and they all come into my MIL's name and all have the PO Box anyway. Most things like that were set up before I moved here :/

next would be....your name on a lease? which I'm sure you don't have either. I'm absolutely no help whatsoever

Can't your MIL write a confirmation that you are living at said address, signed by two witnesses, etc.?

Can you send yourself a letter to your home address?

if I sent myself a letter to my home address, the post office would send it back! To my home address... I would create an infinite loop of stupid.

don't have a lease, no, our apartment was built on the family land!

MIL did do that for the husband, actually. Hmmmm.