Abstract  Nine-to-ten (9210) refers to the problem that the Dutch banks are running out of 9-digit bank account numbers and need to convert to 10-digit numbers. At the same time, the Dutch government wants bank account numbers to be portable to encourage competition; this may become European policy. A recent European standard for cross-border money transfers proposes totally nonportable bank account numbers. These orthogonal policies have such a high IT-soap caliber that we sometimes refer to it as 9210 Policy Nils. Whatever the plot of nine-two-one-o, major challenges are at stake for European banks and other number crunchers like tax authorities, mail-order firms, etc. This paper gives insight in cost aspects, the possibilities, and impossibilities of 9210 and related problems.