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Upcoming changes
The NHI has enough numbers at the current rates of allocation to assign to people until mid 2026. The Ministry is working with the sector to introduce a change to the NHI number format to extend the range of NHI numbers available.
This involves checking and (where necessary) upgrading the health sector’s IT systems which record NHI numbers to accept a new format. This work is underway now to allow time for these checks and any upgrades to take place. It is the responsibility of the digital health suppliers to upgrade their systems to accommodate both, the old and new NHI format, by completing the Compliance Test by clicking here and the NHI Format Change Compliance Form by clicking here.
NHI numbers will start to be issued in the new format from 1 July 2026
What are the format changes?
The existing NHI format is a unique 7-character format AAANNNC (3 alpha, 3 numeric and 1 numeric check digit).
NHI numbers are currently issued sequentially on the first six characters, eg, ZAA0067, ZAA0075, ZAA0083, [...] ZAB0003, ZAB0011, ZAB0020, ZAB0038, and so on.
Once the current format is exhausted, historical gaps in certain letter ranges (H/J/K) will be used until the switch to the new format. The Z-range will be reserved exclusively for testing purposes.
To prevent running out of numbers and future-proof to support population growth, a new format AAANNAX (3 alpha, 2 numeric, 1 letter, and 1 alphabetic check character) will be introduced, expanding the available numbers by approximately 33 million.
The new NHI format will be issued in sequential order of the first letter, starting with As, and then a randomised allocation of the next 5 characters, with the last character an alpha check digit. e.g. ACA31FM, ASE37QK, ARE62RS, […] BGJ06AS, BGA44DT, BWT41BY.
Both formats will coexist. The current format will be used until 30 June 2026, after which the new format will be adopted for all new NHI numbers.
All systems that use, record and store NHI will need to support both formats indefinitely to ensure seamless integration.
This approach is detailed in the updated HISO 10046:2024 Consumer Identity Standard.
What this means for the health sector?
The changes to the NHI number format will have several implications for the healthcare sector, including both challenges and benefits. Here’s what the sector can expect:
Implications for the Sector
- System Upgrades and Adjustments
- IT system changes: Healthcare providers will need to update their IT systems to accommodate the new NHI format (AAANNAX). This includes modifying software for data entry, storage, and processing of NHI.
- Testing and validation: Systems will require testing to ensure compatibility with both the existing (AAANNNC) and new (AAANNAX) formats, including adjustments to validate the new alphabetic check digit.
- Training and education
- Staff training: Healthcare professionals and administrative staff will need training on the new format and any changes to processes. This training will help ensure smooth implementation and ongoing management of NHI numbers.
- Communication Strategies: Clear communication plans will be necessary to inform staff about changes, new procedures, and updates to NHI formats.
- Data management
- Record keeping: Patient records will need to accommodate both the old and new formats. Systems must be able to handle and differentiate between the two formats to ensure data integrity.
- Administrative efforts
- Administrative adjustments: Administrative processes and documentation (where applicable) will need to be updated to reflect the new format, including forms, labels, and reports.
- Coexistence of formats
- Dual format management: All healthcare systems will need to support both the current and new NHI number formats. Systems will need to be flexible and capable of handling two formats simultaneously.
Summary
While the transition to the new NHI format involves significant changes, including system upgrades, staff training, and compliance efforts, it also offers long-term benefits. The new format will ensure the sustainability of the NHI system and support future healthcare demands.
Frequently Asked Questions
What is an NHI?
What is an 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.
What is the NHI format change?
What is the NHI format change?
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.
When will the new NHI format be introduced?
When will the new NHI format be introduced?
The new format will start on 1 July 2026.
Why do we need a new NHI format?
Why do we need a new NHI format?
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.
Why has the check digit algorithm for the new format been changed to use mod 23 instead of mod 24?
Why has the check digit algorithm for the new format been changed to use mod 23 instead of mod 24?
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.
What is required from suppliers to be compliant?
What is required from suppliers to be compliant?
Read important information on Compliance Testing, Compliance Testing Process, Test Data and Compliance Tests and NHI Format Change Compliance Form.
Why was the option selected?
Why was the option selected?
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.
Why will NHI be issued in a random sequence (non-sequential) in the new format?
Why will NHI be issued in a random sequence (non-sequential) in the new format?
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.
What difference will this make for patients/consumers?
What difference will this make for patients/consumers?
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.
What happens if this work isn’t done in time?
What happens if this work isn’t done in time?
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.
How can we run out of NHIs anyway – don’t they go on forever?
How can we run out of NHIs anyway – don’t they go on forever?
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.
Why isn’t Health NZ paying for this?
Why isn’t Health NZ paying for this?
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.
Will we have to go through the same process in another 10 years or so?
Will we have to go through the same process in another 10 years or so?
The new NHI format (AAANNAX) provides a significantly larger pool of unique identifiers, designed to be sustainable for several decades.
Download: NHI records Mod23 - XLSX, 13 KB
Supplementary to the NHI Test Data above.
More information
If you have any questions about the NHI format changes, please contact integration@tewhatuora.govt.nz.