What Do the Eight Digits of an Insurer Number Tell You? — Law-Type Numbers, Prefecture Numbers and Check Digits Read from a Receipt Computer's Implementation (archived 2026-08-30)

Q: What does this research mean for the field?

The 8-digit insurer number on Japanese health insurance cards is structurally composed of law-type, prefecture, per-insurer, and check digits, and its check digit calculation in ORCA's COBOL implementation aligns with the Ministry of Health, Labour and Welfare's guidelines. Novelty: ClaimNovelty.CONFIRMATORY. Consensus alignment: ConsensusAlignment.NEUTRAL.

Go Komura

doi:10.5281/zenodo.22170732

August 30, 2026Open Access

What Do the Eight Digits of an Insurer Number Tell You? — Law-Type Numbers, Prefecture Numbers and Check Digits Read from a Receipt Computer's Implementation (archived 2026-08-30)

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Key Points

Examine the compositional structure of Japanese health insurer numbers and verify check digit calculation logic against medical software implementations.
Analyzed official Ministry of Health, Labour and Welfare guidelines defining the composition of the eight-digit insurer number.
Deconstructed the check digit calculation algorithm and audited the open-source COBOL implementation within the ORCA (Nichi-Rece) receipt computer system.
Categorized the eight digits into a two-digit law-type code, a two-digit prefecture code, a three-digit unique insurer identifier, and a single-digit check digit.
Confirmed that the ORCA COBOL software faithfully implements the prescribed check digit formula to ensure systematic data validation.

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Implication

Technical analysis reveals the numerical structure and validation algorithms in Japanese health insurer cards, highlighting reliable receipt computer implementations.

Abstract

The insurer number on a Japanese health insurance card is made up of a 2-digit law-type number, a 2-digit prefecture number, a 3-digit per-insurer number and a 1-digit check digit. Taking the Ministry of Health, Labour and Welfare's setting guidelines as the primary source, this article takes the structure apart and verifies the check digit calculation and ORCA's (Nichi-Rece's) COBOL implementation against the published source. Archived version of https://comcomponent.com/en/blog/insurer-number-structure/, as published on 2026-08-30. The live article is maintained and may change after this date. First published 2026-07-18.

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Cite This Study

Go Komura (2026) studied this question.

synapsesocial.com/papers/6a954259f20e493292a747d2 https://doi.org/10.5281/zenodo.22170732

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What Do the Eight Digits of an Insurer Number Tell You? — Law-Type Numbers, Prefecture Numbers and Check Digits Read from a Receipt Computer's Implementation (archived 2026-08-30)

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Abstract

Discussion

Cite This Study

What Do the Eight Digits of an Insurer Number Tell You? — Law-Type Numbers, Prefecture Numbers and Check Digits Read from a Receipt Computer's Implementation (archived 2026-08-30)

Key Points

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Abstract

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Cite This Study

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