Using Bank Account Number as a Patient Identifier

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Using Bank Account Number as a Patient Identifier

Author: Mike Henderson,

Last revision date: 12 August 2013

A discussion arose recently on the HL7 Infrastructure and Messaging list server regarding whether it might be appropriate to use a bank account number as a person identifier in data type CX, and, if so, how that might be done.

The question of appropriateness would seem to center on whether bank account number can be persistently associated with exactly one person. To that question the answer would have to be “sometimes,” not always. Joint bank accounts, for instance, are associated with more than one person.

It might thus be argued that bank account – in the same way as, say, address or telephone number, which can also be associated with multiple persons – is not suitable for use as a person identifier. To that objection, a reasonable reply would be that there is a qualitative difference in binding between a bank account number and an address or telephone number:

  • An address or telephone number need not necessarily identify any single person; in theory anyone, at any given time, may live or receive mail at the address, or be in possession of the telecommunications device to which the telephone number corresponds.

  • Put another way, an address identifies a location, and a telephone number identifies a telecommunications endpoint, neither of which need necessarily correspond with any particular person at any point in time, and either of which might correspond with multiple persons over successive and/or overlapping intervals of time.

  • By contrast, a bank account number always intentionally and persistently identifies one or more signatory persons. At least under current United States banking practice, the default procedure (and, at some banks, the only procedure administrated) is that any signatory person may commit funds upon the account. Moreover, neither ownership of the bank account nor assignment of the account number can be casually transferred, as can an address, telephone number or email address.

The remainder of this discussion will thus proceed on the assumption that it is acceptable to use bank account number as a person identifier.

Disambiguation Using Assigning Authority

If it is decided to use bank account number to identify a person, the question arises how to distinguish the account identified by a particular account number from other accounts with the same account number at different banks (and presumably owned by entities other than the person with whom we are immediately concerned).

The use of financial institution as assigning authority (within the CX data type) resolves this issue. Financial institutions have unique, persistent identifiers. In the United States, a Federal or State chartered institution that is eligible to maintain an account at a Federal Reserve Bank may be assigned a routing number by the American Bankers Association. Institutions that engage in international wire transfers also have global identifiers called SWIFT Codes (from the Society for Worldwide Interbank Financial Telecommunication, headquartered in La Hulpe, Belgium) or BIC Codes (Business Identifier Codes). SWIFT Codes, which can have 8 or 11 characters,1 are assigned and administered in accordance with the ISO 9362 Standard.

There is, in addition, an identification scheme called IBAN (International Bank Account Number) that concatenates globally unique institution identifiers with account numbers specific to the institution. This scheme is administered according to the ISO 13616 Standard. While used throughout most of Europe and in a number of developing nations, IBAN is not used in the United States or Canada.

A characteristic that distinguishes IBAN from routing number or SWIFT code – and arguably represents an advantage for IBAN – is that, as a globally unique identifier, IBAN eliminates the need to associate the account identifier with a distinct attribute for assigning authority. However, the lack of adoption of IBAN in North America constricts its usefulness as a globally interoperable identifier. This discussion will thus proceed on the assumption that routing number or SWIFT code is to be used as an explicitly and distinctly expressed assigning authority for a bank account number.

Expressing Account Number Using the CX Data Type

Associating a patient with a bank account number could be accomplished by expressing the account number in an occurrence of PID-3-patient identifier list. The data type of PID-3 is CX (extended composite ID with check digit). Without considering other components of the CX data type, a bank account number could be expressed by inserting the account number into component CX.1 (ID), the routing number or SWIFT Code into component CX.4 (assigning authority) and the literal value BA for “bank account number” into component CX.5 (identifier type).

Expressing Financial Institution as an Assigning Authority

During the list server discussion, some confusion arose as to how the financial institution might be stated as an assigning authority in CX.4. The data type of CX.4, which is HD (hierarchic designator), is particularly suited to this task.

HD allows both a local identifier (called namespace ID) in the first component, which could be the name (full or abbreviated) of the financial institution; and a global identifier (called universal ID) in the second component, which could be the routing number or SWIFT Code.

The third component of HD contains the universal ID type of the global identifier in the second component. For routing number, this could be the literal ABA (for American Bankers Association), while for SWIFT Code this could be the literal ISO9362. If it is deemed appropriate to allow the use of bank account numbers as patient identifiers, it would be highly desirable to add the literal values ABA and ISO9362 to HL7 Table 0301, Universal ID Type.2

Some Examples of Representing Bank Account Numbers in PID-3

Patient has account number 999-8899 at The Provincial State Bank, which is based in the United States. The bank’s routing number is 9997776 and its 8-character SWIFT Code is ZZZZUS9Z. The following examples show several ways in which this information might be represented in components 1, 4, and 5 of an occurrence of PID-3.


Note that component 4 contains three subcomponents, which are the components of data type HD.

9998899^^^PROV ST BANK&9997776&ABA^BA

The first subcomponent of component 4 (which is the first component of data type HD) is taken from user-defined Table 0300, Namespace ID. HL7 is silent as to how individual implementations choose to represent values in user-defined tables. Subcomponents 2 and 3 contain the globally interoperable identifier for the assigning authority.


This example uses the SWIFT Code instead of the routing number.

1 An 11-character SWIFT Code concatenates the institution identifier with a branch or location identifier. An 8-character SWIFT code always refers to the institution’s primary branch or location.

2 It would also be highly desirable in any event to add to Table 0301 the literal value ISO9834-1 to indicate an object identifier (OID), and to deprecate the ambiguous value ISO which is now used to indicate OIDs.

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