Compliance Problems

How to Configure Microsoft Purview Validation for Belgian BBAN Numbers

Camila Milosovich Oct 12, 2026 868 views

Question details

The user needs to configure a custom sensitive information type in Microsoft Purview to detect Belgian Basic Bank Account Numbers (BBAN) using regex and a MOD 97-10 checksum validation.

How to Configure Microsoft Purview Validation for Belgian BBAN Numbers

Product: Microsoft Purview
Device & OS: not provided
Scenario: Creating a custom sensitive information type (SIT) to accurately detect and protect Belgian bank account numbers for enterprise data compliance.
Observed behavior: Uncertainty in differentiating BBAN and IBAN formats, and difficulty configuring the checksum algorithm because the field behaves unexpectedly when entering '97-10'.

Before you start

Ensure you have the necessary Compliance Administrator permissions in the Microsoft Purview portal to create and modify custom Sensitive Information Types (SITs).

Solution 1Recommended

Configure Custom Sensitive Information Type for Belgian BBAN

Set up the correct regular expression and checksum validation to accurately distinguish and detect Belgian BBANs.

It is crucial to distinguish between a Belgian BBAN and an IBAN when writing your regular expressions. A BBAN consists of 12 digits (often formatted as 539-0075470-34 or 539007547034), whereas an IBAN begins with 'BE' and includes two additional check digits. You must use the correct regex for the specific format you intend to catch.

Define the Regular Expression

In the Microsoft Purview compliance portal, navigate to Data classification > Sensitive info types. Create a new SIT and define a regex for BBAN. For a 12-digit BBAN, use a regex like ^\d{3}-?\d{7}-?\d{2}$ to account for optional hyphens.

Select the Checksum Validator

Add a new validation rule to your SIT pattern and select 'Checksum validator'. Since the algorithm field only accepts numbers or predefined functions, do not manually enter text like '97-10'.

Verify Algorithmic Syntax

Consult the official Microsoft Purview documentation for 'SIT Regex Validators'. Purview uses specific built-in functions (such as Func_belgium_bban or similar standard modulo 97 validations) rather than manual weight inputs for European bank accounts.

Test Before Publishing

Save your configuration and upload a test document containing dummy BBAN numbers. Verify that the pattern correctly identifies the BBANs without triggering false positives.

Configure Custom Sensitive Information Type for Belgian BBAN

IBAN Configuration: If your goal is to detect IBANs instead of BBANs, use the regex ^BE\d{2}\s?\d{4}\s?\d{4}\s?\d{4}$ and utilize Purview's pre-configured 'EU Debit Card Number' or built-in IBAN sensitive information types.

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Frequently Asked Questions

What is the difference between a Belgian BBAN and an IBAN?

A Belgian BBAN (Basic Bank Account Number) consists of 12 digits (e.g., 539-0075470-34). An IBAN (International Bank Account Number) for Belgium starts with the country code 'BE', followed by 2 check digits, and then the 12-digit BBAN.

Why can't I enter '97-10' in the Purview checksum algorithm field?

The checksum algorithm field in Microsoft Purview is designed to accept only specific numeric identifiers or predefined validation functions. To validate a Modulo 97-10 check, you must use the supported built-in functions listed in the Microsoft Purview regex validator documentation.

Can I test my custom sensitive information type before deploying it?

Yes, Microsoft Purview allows you to upload a test file within the Sensitive Info Types section. This lets you verify if your newly created SIT accurately detects the BBANs without generating false positives before rolling it out to your policies.

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