---
title: Developer Guides — IBAN, X12, ISO 20022 & GS1 | StanzaAPI
description: Plain-language guides to IBAN structure and check digits, X12 837/835, SNIP validation, ISO 20022 payments, and GS1 Application Identifiers.
canonical: https://stanzaapi.com/guides
---

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# Guides & Explainers

Plain-language reference for the standards the StanzaAPI engines implement: IBAN, ANSI X12, ISO 20022, and GS1.

[What Is an IBAN? Structure, Length, and Check Digits — An International Bank Account Number (IBAN) identifies a bank account across borders. It is a two-letter ISO 3166-1 country code, two ISO 7064 MOD-97 check digits, and a country-specific Basic Bank Account Number (BBAN). — Read the guide (5 min) →](/guides/what-is-an-iban)[How to Calculate an IBAN Check Digit (ISO 7064 MOD-97-10) — IBAN check digits are computed with ISO 7064 MOD-97-10. Rearrange the string, convert letters to numbers, take the integer modulo 97, and subtract it from 98. — Read the guide (4 min) →](/guides/how-to-calculate-iban-check-digits)[ANSI X12 837 vs 835: Claims and Remittance Advice — The X12 837 is a healthcare claim submission; the X12 835 is the electronic remittance advice (ERA) that explains the adjudication. They are two halves of one round trip. — Read the guide (6 min) →](/guides/x12-837-vs-835)[X12 SNIP Validation Levels 1–6 Explained — SNIP is the WEDI framework for testing X12 healthcare transactions. Types 1 to 6 range from EDI syntax and guide compliance through balancing, code-set and payer-specific edits. — Read the guide (5 min) →](/guides/x12-snip-validation-levels)[ISO 20022: pain.001 vs pacs.008 Explained — ISO 20022 messages are grouped by family: pain for payment initiation, pacs for clearing and settlement, and camt for cash management. pain.001 starts the payment; pacs.008 carries it between banks. — Read the guide (5 min) →](/guides/iso-20022-pain-001-vs-pacs-008)[GS1 Application Identifiers (AI) Explained — A GS1 Application Identifier (AI) is a numeric prefix that defines the meaning and length of the data that follows it inside a GS1 barcode, such as a GTIN, batch, expiry date, or serial number. — Read the guide (6 min) →](/guides/gs1-application-identifiers)[How to Validate a VAT Number (VIES and National Registers) — VAT number validation is two different checks: VIES confirms an EU VAT number is registered for intra-EU trade, while a national register confirms a domestic registration. — Read the guide (5 min) →](/guides/how-to-validate-a-vat-number)[What Is an LEI? ISO 17442 Structure and Check Digits — A Legal Entity Identifier (LEI) is a 20-character code that identifies a legal entity worldwide. ISO 17442 defines it, GLEIF-accredited Local Operating Units issue it, and its last two characters are MOD-97-10 check digits. — Read the guide (5 min) →](/guides/what-is-an-lei)[How to Generate Valid Test IBANs for QA and CI — A test IBAN is a mathematically valid IBAN that is not a real bank account. A generator builds one from a country format plus a bank code, then computes the MOD-97 check digits so validators accept it. — Read the guide (4 min) →](/guides/generating-valid-test-ibans)