Hello,
this thread seems to be the right one for my two questions:
1. I am about to move to a new apartment, but before I actually do this I will go home to Europe for about two weeks. I originally planned to go the Immigration Office just before I leave the country, apply for the address change on my ARC, and pick it up after I come back to Taipei (to safe time because I have got to change my mailing address at a couple of institutions and don't want letters to get lost, i.e. be sent to my old address when I no longer live there). However, my roommate just told me that they might first take away my old ARC, which would leave me without ARC for some time (including my leaving and re-entering the country) - that's not so good, right? Does the Immigration Office actually do this? If yes, I suppose I'd better wait until after my trip home for the whole process, right? How long does an address change on ARC usually take anyway?
2. The apartment I'm going to move in is actually on the 5th floor but I don't have my own mailbox, so my mail will go into the one for the 4th floor - which is also what my landlord told me to use as address. I actually don't care about this but I now worry whether the Immigration Office might want to see my lease agreement (where there is written "5th floor") - and then everything might get complicated.

When I first applied for ARC last August, the guy there (at Taipei City) did not want to see any prove that I actually lived at the address I told him, but my friend who registered in New Taipei City had to bring a confirmation from her landlord (which was quite a hassle). Do you have any suggestions what I should do?
Thanks for your help, I appreciate it!