Does my UK passport tell me how many people share my name?

June 19, 2014 4:50 AM

The machine-readable code at the bottom of the id page of a UK passport (starting P<GBR) contains a name on one line, and on the second line a long string of numbers, lots of chevrons and then a two-digit number. My mum claims that this two-digit number indicates the number of people with the same name as me already registered as having a passport. This seems unlikely, but is there any truth in it?

My number decreased between passports and she said this was because one of the other 'me' either died or didn't renew their passport. I don't buy this as an explanation at all, but I just renewed for a third time and have the same number as before, and it made me wonder; she says she heard it from a third party so I can't check the origin of the myth, but would be interested if you'd heard it too/heard a different myth about the numbers.

posted by AFII to Grab Bag (7 answers total)

I've never heard this. I can tell you that mine says 04 and there are almost certainly not three other people with British passports with my name. I'm pretty sure I'm the only person in the world with my name, and it's unlikely any of the others, should they exist, have a British passport (I have a not-at-all British name).
posted by hoyland at 5:02 AM on June 19, 2014

Best answer: For a machine-readable passport, Machine-readable zone row 2, positions 43 and 44 are check digits. The number at position 43 may change if the "personal number" in positions 29–42 changes. The number at position 44 may change if positions 1–10, 14–20, or 22–43 change. Since positions 22–27 are the expiration date of the passport, it's likely (but not certain) that check digit 44 will change with a new passport expiry.
posted by grouse at 5:02 AM on June 19, 2014 [3 favorites]

I've never heard this before, but as a data point, my Irish passport, which as far as I know is to the same EU standard as a UK passport, has a zero in that position. As far as I know, I'm the only person around with my real-life name, so I would certainly expect that there is no one else previously registered with my name.
posted by Azara at 5:04 AM on June 19, 2014

To be clearer, there is no truth to this myth, and there is no need to look into other myths since the meaning of positions 43–44 is produced by a well-documented mathematical formula.
posted by grouse at 5:06 AM on June 19, 2014 [4 favorites]

Response by poster: Oh! grouse may have solved it - my number has been in the pattern: X, X-1, X-1
My first passport was a limited-time/young person's one, while the other two are full 10 year passports, so if it's a renewal/expiration thing that would explain why the first passport had a different number to the second two. Neat!
posted by AFII at 5:07 AM on June 19, 2014

Best answer: The expiration date is a specific day (YYMMDD), not a number of years. So it's possible that position 44 will change again on your next passport, even if it is valid for 10 years. It's effectively coincidence that you got the same number there twice in a row.
posted by grouse at 5:11 AM on June 19, 2014

Yep, like several other people here, mine's not 01, and it would be according to that rule. In general, reverse engineering codes like this is unlikely to be straightforward, and you'll always need to allow for a checksum somewhere. Also, there's likely to be few codes like this where you can't just find out the entire specification on the internet, as shown above. ISBNs, product barcodes and the like all have publicly accessible specifications for you to decode them. It's very neat.
posted by ambrosen at 7:50 AM on June 19, 2014