Upcoming changes to NHI

The National Health Index (NHI) is a unique identifier used in New Zealand's healthcare system to record and track individuals' health information. Each person enrolled in the system receives an NHI number, which is used to access and manage their health records across various healthcare services. This ensures that health information is accurately linked to the correct individual, facilitating efficient and effective healthcare delivery.

New format: To prevent running out of NHI unique identifiers, a new format AAANNAX (3 letters, 2 numbers, 1 letter, and 1 alphabetic check character) will be introduced, expanding the available NHI range by approximately 33 million.

Current format: The existing NHI number format is AAANNNC (3 letters, 3 numbers, 1 numeric check digit). The H/J/K numbers will only be used to bridge the gap between the end of the current format Y range and issuing the new format from 1 July 2026.

Transition: From 1 July 2026 both formats will coexist.  The current format will be issued until 30 June 2026, after which the new format will be used for all new NHI numbers.

If the current NHI format runs out prior to July 2026, historical gaps in the H/J/K letter ranges will be used to issue new NHIs until the new format is introduced.

Implementation: Systems will need to support both formats indefinitely to ensure seamless integration. Detailed in the updated HISO 10046:2024 consumer health identity standard.

Testing range: The Z-range will be reserved exclusively for testing purposes.

The new format will start on 1 July 2026.

Exhaustion of current format: The current NHI format (AAANNNC) is running out of available unique identifiers. Without a new format, the healthcare system will soon be unable to issue new NHI numbers, crucial for registering new patients and maintaining accurate health records.

Population growth: New Zealand’s growing population, through births and immigration, increases the demand for unique NHI numbers.

Futureproofing: The new format (AAANNAX) adds approximately 33 million new combinations, ensuring the healthcare system can issue NHI numbers for several more decades without interruption.

System efficiency: Proactively updating the format now ensures a smooth transition, preventing potential disruptions in healthcare services if the current format is exhausted.

Compatibility and minimal impact: The new format retains the seven-character length, minimising impact on existing healthcare systems, databases, and workflows.

Regulatory and standards compliance: Updating the NHI format aligns with evolving health information standards and regulatory requirements, ensuring compliance and interoperability with international best practices.

Implementation and testing of the new check digit algorithm identified a weakness with the algorithm which means it failed to identify an unacceptably high number of character substitutions. In recognition that we have one chance to get this right before the new NHI number format starts to be issued, we have changed the check digit algorithm to use a modulus 23 operator, rather than a modulus 24 operator, retaining the existing sequence of factors (7, 6, 5, 4, 3, 2). This will reduce character substitution detection failures from an unacceptably high rate of 7%, to approximately 0.2%. Importantly, it also resolves an issue where “1” and “7” could be freely substituted in the number section of the NHI.

Not every IT system that stores the NHI validates the check digit, however those that do will need to ensure they are using a modulus 23 operator, rather than a modulus 24 operator, when calculating the check sum. An updated version of the HISO 10046:2024 consumer health identity standard was published on 22 July 2024 describing this change.

Read important information on Compliance Testing, Compliance Testing Process, Test Data and Compliance Tests and NHI Format Change Compliance Form.

In 2017, the NHI support team identified a preferred option and referred it to the Health Information Standards Organisation (HISO).

In 2018, a formal public comment process was conducted, receiving overwhelming support for the recommended option.

Futureproofing the NHI system: The new format (AAANNAX) expands the number of unique identifiers, offering approximately 33 million new combinations to meet the needs of New Zealand’s population for several decades.

Broad support from stakeholders: Feedback from the 2018 public comment process showed broad support from healthcare providers, administrators, and the public.

Minimising disruption: The new format maintains the seven-character length, ensuring minimal disruption to existing healthcare systems.

Alignment with best practices: The selected option aligns with international best practices for health information standards, including random allocation of NHI numbers to protect identities.

Issuing NHI in a random sequence enhances security and privacy, prevents predictable patterns, and maintains the integrity of the NHI system. For example, in the case of multiple births, random sequencing can ensure privacy and reduce confusion between identities.

The transition to the new NHI format will be seamless for patients, with no disruption to medical records, healthcare services, or ongoing treatments. Patients do not need to take any action.

Delays could lead to exhaustion of the current NHI format, disruption in healthcare services, data management challenges, administrative burdens, compliance issues, and increased costs.

It is crucial to adhere to the timeline and implement the new NHI number format by 1 July 2026.

The current format has a limited number of combinations (17,576,000), which is not infinite. Population growth and the need for unique identifiers necessitate a new format to ensure continued operation.

Implementation costs are expected to be absorbed by software suppliers or addressed contractually between software users and providers.

This approach is based on the principle that the NHI is a fundamental health system standard, with vendors typically covering maintenance and support changes.

The new NHI format (AAANNAX) provides a significantly larger pool of unique identifiers, designed to be sustainable for several decades.