So I am leaving for a business trip to the U.S. soon, and Japan has just adjusted its immigration laws and procedures. One welcome change: re-entry permits are no longer required.

However, there are other details as well. Rules are different between regular visa holders and those with permanent residency. And there’s a new “Residence” card to replace the “Alien Registration Card.”

I have not had time to get the new card, and after all, I am not required to change until 2015. My last re-entry permit expired, but they say you don’t have to have one any more. Feeling my “Gaijin-ey Sense” tingling, I wanted to make sure: if I travel outside of Japan without a new Residence card and without an old-fashioned re-entry permit, am I still OK?

I called Immigration in Shinagawa to make sure, and they said “yes.” I called the Narita office, and they repeated the same thing. Still paranoid, I called the main immigration office again and spoke with a supervisor. Same answer.

Just to be on the safe side, I spoke with an advisory center for foreigners, who told me the same thing, but added one tiny little detail: on the embarkation-disembarkation card they have you fold inside your passport, a new check box has been added: it reads, “みなし再入国許可” and “Departure with Special Re-entry Permission.”

If you don’t check that box, you lose your visa status, including your permanent residence status.

I called Narita once more after learning that, and they gave me the same vague reassurances they had before. I asked if there was anything else, they said “no.” I then asked about the check box. The guy said, “Oh yes, You have to do that too.”

Well, thanks for giving me the heads-up on that.

Okay, maybe they make sure you check the box at the airport. Or maybe it’s something everyone must do and they did not think of mentioning it in answer to my specific question.

And yet, with the consequences as dire as that for such a tiny little detail, one would think they would mention it in passing. You know, “Just make sure to check the ‘re-entry’ box on you E-D card!” To which most people would reply, “The what on my what?”

I really have to wonder how many people are going to walk into major trouble because that detail is glossed over.