The Finnish national personal identification number is the Henkilötunnus, aka Hetu or Ht, has the following format – ddmmyyc999C. For details how to calculate the control character, I refer to the overview blog on National Identification Numbers.

Validating the Hetu 270368A172X shows that it is indeed a correct number. The number 270368172 generates indeed 29 for the modulo 31 proof, represented by control character “X” in the checksum list. The number shows that this is the 86-th girl born on the 27th of March 2068.

The latter might is exactly the start for the discussion on validity. Althought the number itself is well formed, and passes all the automatic checks, dealing with this number in a data quality assessment will raise your digital eyebrow. In the data quality world we will nowadays say that this Hetu is a wrong Hetu, that it cannot be correct.

So always use a bit of human inference when dealing with finnish national personal identification numbers.